British police said evidence at the home of Boris Berezovsky, an exiled Russian oligarch who was found dead near London on Saturday, does not indicate "third party involvement."

“It would be wrong to speculate on the cause of death until the post mortem has been carried out. We do not have evidence at this stage to suggest third party involvement,” Detective Chief Inspector Kevin Brown, Deputy Senior Investigating Officer in the case, said in a statement.

Berezovsky, 67, amassed a mammoth fortune as an oil and automobiles magnate during Russia’s post-Soviet privatization of state assets in the early 1990s. He also accrued immense political influence, catapulting Boris Yeltsin to re-election in 1996 and brokering Vladimir Putin’s rise to prominence.

But when Putin became president of Russia in 2000, Berezovsky became one of his harshest critics and often clashed with the Kremlin. He soon fled to Britain, where he was granted political asylum three years later.

Police said the tycoon’s death was “unexplained” and are working to make sense of Berezovksy’s final hours.

“The investigation team (is) building a picture of the last days of Mr. Berezovsky’s life, speaking to close friends and family to gain a better understanding of his state of mind,” said Brown.

Authorities announced Sunday that radioactive, biological and chemical specialists sent to conduct tests gave the scene an “all clear,” The Associated Press reported.

“Officials found nothing of concern in the property, and we are now progressing the investigation as normal,” according to the police statement.

Heightening the intrigue is the fact that Berezovsky was a close friend of Alexander Litvinenko, a Russian dissident who was fatally and mysteriously poisoned with radioactive polonium in London in 2006.

Berezovsky was an outspoken opponent of Putin in recent years, charging the president with dictatorial policies and domestic terrorism. Berezovsky, who survived assassination attempts – including a bombing that decapitated his driver – said he feared retributive violence after criticizing the government, according to Reuters.

A spokesman for Putin on the Russia 24 television station said that he was not aware of the president’s reaction to the news of Berezovsky’s death, but that “news of anyone’s death, no matter what kind of person they were, cannot arouse any positive emotions.”

NBC News’ Becky Bratu contributed to this report.

Paul Hackett / Reuters, file

Britain's Jemima Khan, supporter of WikiLeaks' founder Julian Assange, arrives at Belmarsh Magistrates' Court in London Feb. 24, 2011. A court is expected to rule on Thursday whether Assange should be extradited to Sweden where he is accused of sex crimes.

Published at 4:20 p.m. ET: LONDON - Jemima Khan, a celebrity backer of Julian Assange who put up bail money for him, has gone public with her frustrations about the WikiLeaks founder, saying he demands "blinkered, cultish devotion" and should face justice in Sweden.

An article by Khan published on Wednesday on the website of British magazine The New Statesman gives an insight into how Assange, whose whistleblowing website angered Washington by releasing thousands of U.S. diplomatic cables in 2010, has alienated some of his staunchest allies.

Assange was arrested in Britain in December 2010 on an extradition warrant from Sweden, where he is wanted for questioning over allegations of rape and sexual abuse made by two women.

After losing a protracted legal battle to avoid extradition, which went all the way to Britain's Supreme Court, Assange jumped bail and sought refuge in the Ecuadorean embassy in London last June. He has been inside the building ever since.

Khan, who first rose to prominence as an heiress but is now a campaigner and an associate editor of The New Statesman, described in her article how she had gone from "admiration to demoralization" on the subject of WikiLeaks.

"The problem is that WikiLeaks - whose mission statement was 'to produce ... a more just society ... based upon truth' - has been guilty of the same obfuscation and misinformation as those it sought to expose, while its supporters are expected to follow, unquestioningly, in blinkered, cultish devotion," she wrote.

'We Steal Secrets'
Khan was executive producer of a documentary film about WikiLeaks entitled "We Steal Secrets" which recently premiered at the Sundance Film Festival in the United States.

Philip Toscano / AP

Julian Assange addresses the Oxford Union via video-link from the Ecuadorian Embassy in London, Wednesday Jan. 23, 2013. WikiLeaks founder, Julian Assange, currently living as a fugitive in the Ecuadorian Embassy in London where he has been granted political asylum in reaction to an alleged 2010 sexual assault in Sweden, and will addresses the 189-year-old Oxford Union debating society, delivering his address via video-link.

Khan said the film, directed by Oscar-winning documentary maker Alex Gibney, sought to present a balanced view of the WikiLeaks story but Assange had denounced it before seeing it.

"When I told Assange I was part of the We Steal Secrets team, I suggested that he view it not in terms of being pro- or anti-him, but rather as a film that would be fair and would represent the truth," she wrote. "He replied: 'If it's a fair film, it will be pro-Julian Assange.'"

Khan's article praised WikiLeaks for exposing corruption, torture, war crimes and cover-ups but criticized it for a "with us or against us" mentality that was detrimental to its cause.

She wrote that she was among those who had found the timing of the sexual abuse allegations against Assange suspicious, as they came at the height of the furor over the revelations on WikiLeaks, but had come to the conclusion that the allegations had to be dealt with through Swedish due process.

"The women in question have human rights, too, and need resolution. Assange's noble cause and his wish to avoid a U.S. court does not trump their right to be heard in a Swedish court," she wrote, referring to Assange's fears that Sweden could be a first stop on the way to an espionage trial in the United States.

"I don't regret putting up bail money for Assange but I did it so that he would be released while awaiting trial, not so that he could avoid answering to the allegations," Khan wrote.

Khan has not disclosed how much money she put up and whether she has had to surrender it since Assange skipped bail.

Khan wrote that it was hardly surprising that a man who had spent his life "committed to this type of work, wedded to a laptop, undercover, always on the move", would have an unusual personality.

"I have seen flashes of Assange's charm, brilliance and insightfulness - but I have also seen how instantaneous rock-star status has the power to make even the most clear-headed idealist feel that they are above the law and exempt from criticism."

Related:

Supporters of WikiLeaks' Assange lose $320,000 in bail money

UK refuses WikiLeaks' Assange safe passage to Ecuador

US documents reportedly refer to Assange, WikiLeaks as 'enemy'

Carl Court / AFP - Getty Images

'Femme assise pres d'une fenetre' (A woman sitting by a window) by Spanish artist Pablo Picasso, sold for $45 million at Sotheby's auction house in central London.

LONDON -- A Pablo Picasso portrait of his mistress and "golden muse" Marie-Therese Walter sold for $45 million on Tuesday, leading an important Sotheby's auction of impressionist, modern and surrealist art.

The sale was the first of a series held in London this month by Sotheby's, Christie's and smaller auction houses in the latest barometer of the strength of the high-end art market.

Prices for the most sought-after works have soared in recent years despite broader economic concerns, with collectors in China, Russia and the Middle East joining more established patrons in Europe and the United States.

Subtracting the buyer's premium of more than 10 percent, the amount realized for the 1932 Picasso was at the lower end of pre-sale estimates of $39 million-$55 million.

Nonetheless, it was comfortably the top lot of an evening when a series of works on paper by Austrian artist Egon Schiele arguably stole the limelight.

Schiele's 1914 "Lovers (Self Portrait With Wally)" fetched $12 million, an auction record for the artist for a work on paper.

Also sold by the Leopold Museum in Vienna was his "Self Portrait in Green Shirt with Eyes Closed" which sold for $8 million, well above expectations of between $3 million and $4 million.

The combined tally for Schiele works, sold by the museum to help settle a long-running restitution case involving art deemed to have been stolen by the Nazis in the 1930s, was $22 million.

'Strongest offering in many years'
Other lots fared less well, notably Max Beckmann's "Before the Ball - Two Women With a Cat" which went unsold despite pre-sale estimates of $8 million-$13 million.

Overall the evening brought in $189.4 in sales, within expectations of $161 million-$233 million. Sotheby's said it was their second highest total from an equivalent sale in London.

"Bidders, both new to the market as well as seasoned buyers, reacted with great enthusiasm, in particular to the selection of impressionist works that were considered to be the strongest offering in many years," said Helena Newman, chair of Sotheby's impressionist and modern art in Europe.

Christie's, the world's largest auction house, holds its sale in London on Wednesday.

Related: 

Art sleuth recovers stolen Matisse

Rare drawing by Raphael sells for record $48 million

Rockwell painting sells for $2.8 million

LONDON – London’s legendary blue plaques -- historical markers commemorating the lives of eminent figures -- face an uncertain future because of austerity cuts at England’s official heritage agency.

More than 850 ceramic signs honor key people who lived in the U.K. capital, and their contribution to human history.

Toby Melville / Reuters (file)

One of London's 869 blue historical markers.

But the program -- almost 150 years old and believed to be the first of its kind in the world -- now faces a “very uncertain future,” according its lead administrator at English Heritage.

“These are extremely difficult times for English Heritage and for the scheme,” wrote Emily Cole in a letter made public earlier this month.

Existing plaques will remain, but no new locations are planned and the panel of historians and experts that considers nominations for future signs has been suspended.

The news has been greeted with dismay in London.

“Blue plaques are one of the most charming ways a capital has ever found to preserve historical memory,” cultural commentator Jonathan Jones wrote in The Guardian newspaper. “They eschew the pomposity of statues.”

David Tucker, who leads thousands of tourists on guided walks of London every year, told NBC News: “The plaques are part of the fabric of the city and it’s such a shame.

“As an American living here for 30 years, I can say that I still find myself coming across plaques I have never seen before and learning new things.”

The earliest surviving plaque, erected in 1867, marks the building in King Street where French emperor Napoloeon III once lived. (The first, erected the same year to commemorate the birthplace of Lord Byron, was lost when that building was demolished in 1889.)

In total, the city is dotted with 869 circular, domed signs. Among those honored are Americans with London connections including Jimi Hendrix -- who lived on Brook Street while recording 'Electric Ladyland' -- author Mark Twain, inventor Samuel Morse and broadcast journalist Edward Murrow.

Similar historical markers now exist elsewhere in England in many other cities around the world, including in the United States through bodies such as the New York Landmarks Preservation Commission.

“Over the next eighteen months, we will work up the details of a new and more cost-effective approach to its administration,” said Ellen Harrison, a spokeswoman for the English Heritage, adding that it would need to “become more cost effective and more self-sustaining.”

Each sign costs $1,500 to manufacture and a further, variable, sum to install, while the overall program costs $400,000 a year to operate.

English Heritage last year generated around $86 million from membership subscriptions and admission fees at its historic sites. But it is still heavily reliant on public cash, and faces a 34 percent cut in its grant from Department for Culture, Media and Sport, from $218 million in 2010 to $147 million in 2014, as the U.K. government struggles to reduce a huge budget deficit.

One plaque marks the site of the studio used by sculptor Sir William Reid Dick, who wrote that buildings are “more than just bricks and mortar…they are the theaters in which our lives are enacted.”

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A foul-smelling cloud of gas escaped from a factory in northern France on Tuesday, making life unpleasant from the outskirts of Paris to Britain's shores and prompting scores of emergency calls.

France's Interior Ministry released a statement saying the mercaptan gas escaping from the Rouen chemical factory is harmless. Among other uses, mercaptan is added to otherwise odorless municipal gas to alert people of leaks. The factory has been shut down, and environmental authorities are carrying out tests.

While authorities reassured residents no to worry, winds carried the smell across hundreds of square miles.

Police in the coastal English town of Hastings reassured residents in a tweet with the hashtag "noneedtopanic" that mercaptan from Rouen was the likely cause of the odor.

The London Fire Brigade tweeted that it had received five times as many calls about potential gas leaks before 10:30 Tuesday morning than it had taken all of the day before. The response? Hashtag "mondieu."

The factory in the northern city of Rouen is owned by Lubrizol, a subsidiary of investor Warren Buffett's Berkshire Hathaway.

"Bearing in mind the lack of danger, residents of the areas concerned are asked not to call emergency services," the Interior Ministry said.

Charly Triballeau / AFP - Getty Images

A gas leak at this chemical plant in the Normandy city of Rouen could be smelled as far away as Paris and London. Officials say it is harmless.

The local government posted a message on its website, asking people not to call emergency services and instead set up a hotline to answer questions about the smell.

Pierre-Jean Payrouse, the director of internal operations for the factory, said he hoped the leak would be stopped by Tuesday evening.

But not in time for a French Cup soccer game scheduled for the evening; authorities postponed the Marseille-Rouen match.

LONDON -- London's Heathrow Airport canceled a fifth of flights and airlines scrapped 40 percent of flights to Paris' main airports as snow continued to blanket parts of Europe, with more forecast.

Air France predicted more cancellations on a similar scale for Monday.

Heathrow Ltd, which is owned by Spain's Ferrovial, said the reduced schedule -- amounting to about 250 fewer flights -- would help it cope with the expected snowfall without making further cancellations.

As snow continued to fall through Sunday, the airport operator said Monday's flight schedule would be cut by 10 percent. That number could rise, depending on conditions at other European airports, Heathrow said.

The Paris airport operator, ADP, said airlines scrapped 40 percent of flights into and out of the two main airports on the outskirts of Paris, Charles de Gaulle and Orly, primarily reducing short-haul services. 

London's smaller Stansted and Gatwick airports said they were operating as normal on Sunday morning but that delays and some flight cancellations were likely. 

Weather forecaster the British Met Office said snow was likely to continue into Monday. As much as eight centimeters was expected in southeast England on Sunday, it said.

On average, some 1,300 flights leave Heathrow daily. The airport, Europe's busiest, operates at close to full capacity after Britain's coalition government blocked development of a third runway in 2010. 

Heathrow has spent 36 million pounds ($57 million) on upgrading its winter weather equipment since 2010 -- a year that saw it face heavy criticism after it almost shut down when snow hit just before Christmas. It now has 130 snow-clearing vehicles. 

More than 400 flights were canceled on Friday, while on Saturday 111 flights, most of them operated by IAG's British Airways, were canceled and hundreds of passengers spent the night in Heathrow's terminals. 

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BA said there had been a knock-on effect because many of its planes were in the wrong place after Friday's snow.

"Like other airlines at Heathrow we have complied with a request to reduce our schedule by 20 percent on Sunday and we continue to work with Heathrow Airport to help keep the airport running as smoothly as possible," BA said in a statement. 

"We are doing everything we can to help customers whose flights have been disrupted by severe weather."

PhotoBlog: Hundreds of flights canceled at Heathrow due to snow

Services by Air France-KLM, Ireland's Aer Lingus and Germany's Lufthansa have also been affected. 

France's SNCF railway company announced delays of up to 40 minutes on many lines as drivers were ordered to reduce speed as a safety measure. 

Local media said some 25,000 homes lost power in southwestern France. 

($1 = 0.6304 British pounds)

Additional reporting by Rosalba O'Brien in London, and Brian Love and Gerard Bon in Paris.