Chunks of metal the size of a cellphone fell onto cars in a neighborhood near Toronto airport Monday, around the same time as an Air Canada Boeing 777 made an emergency landing, CBC reported.

The airliner, bound for Japan, suffered a failure in one of its engines shortly after takeoff from Pearson International Airport.

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The plane dumped fuel before returning to Pearson, landing normally using one engine. No injuries were reported.

The aircraft is thought to be fitted with GE90 engines. (GE is part-owner of NBC Universal, which is joint parent company of msnbc.com).

At least four vehicles were hit by pieces of metal, according to Peel regional police Constable George Tudos, but there was no immediate confirmation the debris was from the plane.

“We believe it is, but it's not up to us — we're not the investigating body,” Tudos told CBC.

"As it [the plane] was traveling away from Pearson we had other complaints stating that debris, consisting of metal objects, was falling from the sky," he said.

On Twitter, residents near the intersection of Derry and Kennedy Roads in Mississauga were posting photos of a vehicle’s rear windshield that was apparently smashed by falling material from the plane, Canada's National Post reported.

CBC said there were 318 passengers and 16 crew aboard Flight AC001, which took off from Pearson at 2:10 p.m. ET and returned to make its emergency landing at 3:53 p.m. ET.

Air Canada spokesman Peter Fitzpatrick said the plane's crew requested the emergency landing shortly after takeoff.

A businessman who was on board the plane tweeted that passengers were told it was an engine overheating.

"Seems my plane fell apart! Luckily we managed to land it," Jason Flick tweeted, adding that the plane spent 20 minutes dropping fuel.

The passengers were given hotel accommodation overnight and were expected to resume their journey Tuesday.

The Associated Press contributed to this report.

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LONDON -- The bells of St Clement Danes Church on The Strand chimed on the hour at 10 a.m.  Gray clouds hung low over traffic-filled streets and the cold chilled to the bone.

So a pretty typical February day in central London.

It became untypical at around 11, after two young men walked out of nearby Aldwych underground, or subway, station.  A few minutes later, a public announcement instructed everybody to leave the building. The trickle of commuters leaving the station became a torrent.  Some of them were irate, demanding an explanation from subway workers and police.  Others held their heads or limbs, seemingly wounded and in shock.

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Sirens screamed and a helicopter hovered above.  Police vans, ambulances, fire trucks and a large green tent for the wounded clogged the narrow lane outside the station.  Dozens of first responders -- fire fighters in helmets and black-and-yellow outfits, ambulance workers, police officers and delighted-looking bomb-sniffing dogs -- milled around on the street.

The bad news: Word was that an explosive device had partially detonated deep in the Tube.

The good news: It was all part of a two-day drill on Wednesday called Operation Forward Defensive involving thousands of emergency personnel and volunteers.

Dozens of journalists and officials were observing an exercise of how emergency services, London City Hall, transport officials, Olympic organizers, the government and counter-terrorism units would react to a terrorist attack during this summer's games. According to the scenario, there had been an "incident" in Oxford Street Station, a major transport artery, on August 8, 2012, judged to be one of the busiest days during the Olympics.

"We are preparing on the basis of a severe level of threat that is higher than our current threat level," James Brokenshire, a government minister for security, told NBC News on Monday.

While authorities emphasized that security drills happen all the time, the Olympics doesn't happen all the time.  The eyes of the world will be on London this summer: The city's population is expected to balloon by almost one million and an estimated four billion globally are expected to watch the games on television.

Al-Qaida to Occupy: UK preps Olympics security

Partly because al-Qaida and related jihadi groups, right-wing extremists and Northern Irish militants are all thought to be a threat, the games will see the U.K.'s largest peacetime security operation involving tens of thousands of security officials. 

The issue of security is particularly relevant to Olympics organizers. The decision to award the 2012 games to London was announced on July 6, 2005.  The following morning, the city suffered its worst peacetime attack when four suicide bombers killed 52 commuters, many of them on the subway.

A constant refrain among the phalanx of officials at the drill on Wednesday was improved communications, seen as one of the failings in the response to 7/7, as the July, 2005, attacks are known.

"We are testing our coordination in working with other agencies," said Nicola Watson of the British Transport Police.  "We are testing the communications systems on the underground service, we are testing our command and control in conjunction with the other organizations, and also we are testing the investigation into an incident t such as this."

So a major improvement has been the deployment of a digital radio system that allows first-responders to communicate more effectively and when in subway.

But the drill was a confidence-building exercise as well.

"It's ... about showing that London is ready, and demonstrate it to the world, because a world event is coming to London in a few months," David Whiting of the London Fire Brigade said.

Olympic housing crunch: London landlords evict tenants to gouge tourists

One person whose confidence apparently had been boosted by the drill was London mayor Boris Johnson.

"I want (everybody) to know that London's underground system is the safest in Europe," he said.  "It's never been so safe." 

LIMA, Peru -- Peruvian President Ollanta Humala has declared a 60-day state of emergency to quell increasingly violent protests over the country's biggest investment -- a $4.8 billion gold mine -- by peasants who fear it will damage their water supply, according to reports Monday.

The state of emergency restricts civil liberties such as the right to assembly and allows arrests without warrants in four provinces of Cajamarca state.

That area has been paralyzed for 11 days by protests against the Conga gold-and-copper mining project. U.S.-based Newmont Mining Corp. is the project's majority owner.

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Dozens have been injured in clashes between police and protesters, some of whom have vandalized Conga property. A general strike also shuttered schools and snarled transportation as protesters mounted roadblocks.

Humala said in a brief televised address late Sunday night that protest leaders had shown no interest "in reaching minimal agreements to permit a return of social peace" after a day of talks in Cajamarca with Cabinet chief Salmon Lerner, who had been accompanied by military and police chiefs and was guarded by hundreds of heavily armed police.

• PhotoBlog: Peru's highlanders protest mine project

Humala said the government "has exhausted all paths to establish dialogue as a point of departure to resolve the conflict democratically" and blamed "the intransigence of a sector of local and regional leaders."

Cajamarca state's governor, Gregorio Santos, who has been leading the protests, called Humala's announcement an unnecessary provocation.

'Bloodbath' fear
He said protest leaders had been planning to end the strike and had asked government officials for 12 hours to consult with protesters.

"I think what's being sought is for this to end in a bloodbath," Santos told The Associated Press by telephone. Police have already used tear gas and bullets against protesters.

"We will continue with our fight," Santos added, without specifying how.

• Digging for gold, children paid with bags of dirt

A local environmental group, regional mayors, and the president of the region of Cajamarca say the Conga mine would displace a string of alpine lakes with reservoirs and hurt farmers.

Other protesters worry about not getting what they say is their share of direct economic benefits from the mine.

Newmont announced last week that it was suspending work at Conga until order could be restored.

Its chief executive, Richard O'Brien, said in a statement then that if Newmont was unable to continue with Conga, "the scale and diversity of Newmont's global portfolio" would allow the Denver-based company to "reprioritize and reallocate capital" to "alternatives in Nevada, Canada, Ghana, Indonesia and Suriname."

Newmont has said its environment plan for the mine, which was approved a year ago by the government, meets the highest standards in the mining industry.

$15 billion in gold deposits
It also runs extensive community outreach programs out of its nearby Yanacocha gold mine, some of which were developed after a mercury spill in 2000 that angered local residents.

One protest leader in Cajamarca, Milton Sanchez, told the AP on Sunday night that "this government that has put itself on the side of mining companies and distanced itself from its electoral promises."

"We are not radical," he added. "It's just that the Conga project has not legitimacy in the eyes of the people."

The Conga project, which Newmont owns with Peruvian precious metals miner Buenaventura, would produce 580,000 to 680,000 ounces of gold a year and open in 2014.

It has gold deposits worth about $15 billion at current prices and sits 13,800 feet high in the Andes, about 600 miles north of Lima.

The Associated Press and Reuters contributed to this report.