NEW YORK -- Federal prosecutors on Thursday revealed charges that accuse a Tunisian man who had lived in Canada with applying for a visa "to remain in the United States to facilitate an act of terrorism." 

The charges name Ahmed Abassi, a native of Tunisia who had been living in Canada.  Prosecutors say he came to New York in mid-March. 

Federal investigators say he met with the men involved in a plot -- first revealed in mid-April -- to attack an Amtrak passenger train from New York to Toronto.  They say the plotters discussed blowing up a bridge at Niagara Falls to cause the train to plunge into the gorge below. 

Canadian authorities announced in mid-April that the plot had been stopped. They disclosed then that they had arrested two men -- Chaieb Esseghaier of Montreal, a 30-year-old Tunisian graduate student who is reported to have guerrilla warfare training and is described as the ringleader, and Raed Jaser of Toronto, 35, a school bus driver.

Frank Gunn / AP

Chiheb Esseghaier, one of two suspects arrested last week in Canada in connection with the alleged terror plot to derail a passenger train near the U.S.-Canada border, arrives at Buttonville Airport outside Toronto on April 23.

Federal prosecutors from the Southern District of New York said Thursday that Abassi was arrested 17 days ago. The fact that word of his arrest was withheld indicates he was likely providing some information about the plot to investigators. 

He is charged with fraudulently applying for a work visa "in order to remain in the United States to facilitate an act of international terrorism," according to a statement from the Justice Department. 

Authorities in Canada said in April that an al Qaeda facilitator in Iran had worked with Esseghaier, and also that the train they intended to target was an Amtrak train originating in New York's Penn Station. 

"Esseghaier was simply a bad guy, and dangerous. This guy was purely evil," said one investigator, and had scientific training and the technical ability to make chemical bombs. 

Law enforcement officials say Esseghaier met Abassi during a trip to New York. But they say the meeting did not go well.  Abassi, they say, thought he should be the person in charge. As a result of the failure to get along, Abassi did not have a role in the derailment plot. Authorities did not spell out any further the basis for the visa fraud charge beyond saying it was to facilitate an “act of terror.” 

The FBI has covertly monitored the activities of the two Canadian men, their contact with overseas Al Qaeda facilitators and others, and their possible connection to others who could be linked to the plot. 

"What Mr. Abassi didn't know was that one of his associates, privy to the details of the plan, was an undercover FBI agent," said George Venizelos, the FBI Assistant Director in Charge of the New York office. 

The yearlong covert investigation involved electronic and physical surveillance. Authorities emphasize, however, that this was no sting operation.  It was, they say, a significant terror plot, once which failed to get more notice because of the Boston Marathon bombings. 

CTV News via Reuters

Raed Jaser is seen arriving at court in the back of a police car in Toronto on April 23.

Esseghaier and Jaser made their initial court appearances in Canada in April. They are charged with conspiracy to commit murder, conspiracy to interfere with transportation and participating in terrorist group activities. Esseghaier told the court that the Criminal Code of Canada “is not a holy book” and did not apply to him.

Richard Esposito is senior executive producer of the NBC News investigative unit; Jonathan Dienst is WNBC chief investigative reporter and NBC News contributing correspondent in New York City; Pete Williams is NBC News justice correspondent.

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EPA

Paramedics tend to some of the people injured when two trains collided near Pretoria, South Africa, on Thursday.

JOHANNESBURG, South Africa — At least 150 people were injured on Thursday when two commuter trains collided near the South African capital of Pretoria, authorities said.

The accident occurred when a train crashed into a stationary locomotive near Attridgeville, a suburb west of Pretoria.

"Many are walking wounded and already left. There are 20 people in serious condition and one, the driver of the second train, is in a critical condition," local emergency services spokesman Johan Pieterse said.

Officials said that children were among the wounded.

Evert Elzinga / EPA

Rescue workers evacuate injured passengers at the scene of a train collision near Amsterdam on Saturday.

AMSTERDAM -- Almost 125 people were injured, many seriously, when two Dutch commuter trains crashed head-on in Amsterdam on Saturday, police said.

There were no immediate reports of fatalities, but of those injured, 13 suffered major injuries while 43 or 44 were badly injured, a spokesman said. About 70 suffered minor injuries.

A trauma helicopter was used to bring the injured to hospital, a spokesman for railways group NS said.

The trains did not serve Schiphol international airport, the NS spokesman added, but the accident disrupted airport train service.

Some people were lifted from the wreckage by cranes while others were led away from the crash site in protective wraps to dozens of waiting ambulances, while police cars and fire trucks stood by.

"We heard a loud bang. I went outside and saw people on the street in panic," a woman at the scene told broadcaster AT5.

"We then saw what had happened. Quite quickly there were emergency services at the scene. It was managed well. Some people had head wounds, others were limping."

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One of the trains involved in the crash serves the cities of Den Helder and Nijmegen, while the other runs between Amsterdam and Uitgeest, the railways spokesman said.

Netherlands public broadcaster NOS aired video footage showing two trains that had collided.

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