Shaun Best / Reuters file A Via Rail Canada passenger train pulls into Dorval Station in Montreal, in this July 22, 2009 file photo. Canadian police authorities said on Monday they had arrested and charged two men with an "al Qaeda-supported" plot to derail a passenger train.

Canadian security forces say they have thwarted an al-Qaeda-backed plot to blow up a rail line between Canada and the United States, and officials announced two arrests on Monday afternoon.

Canadian authorities hold a press conference after two men were arrested and charged in an alleged "al Qaeda-supported" plot to blow up a U.S.-Canada rain line.

The suspects had sought to attack a passenger train that left from the U.S. bound for Toronto once the train crossed the Canadian border, sources told NBC News. The suspects may have scouted trains departing from New York.

Canadian officials worked closely with the FBI throughout the investigation, which began last year.

Royal Canadian Mounted Police announced the two accused, Chiheb Esseghaier, 30, of Montreal, and Raed Jaser, 35, of Toronto, were conspiring to carry out a terrorist attack against a "VIA Rail Canada" passenger train. VIA runs trains in partnership with Amtrak.

Authorities said the men were planning to attack a route, not necessarily a specific train.

Exactly how the men planned to attack was still unclear, only that it was a threat to kill people, officials said.

The men were receiving support from al-Qaeda elements in Iran, according to officials, who added that there was no information to indicate the support was state-sponsored.

Charges against the pair include conspiring to carry out an attack against, and conspiring to murder persons unknown for the benefit of, at the direction of, or in association with a terrorist group, officials said. Police were searching the suspects homes Monday afternoon.

The men "had the capacity and intent to carry out these criminal acts," but "there was no imminent threat to the public, rail employees, train passengers or infrastructure," James Malizia, assistant commissioner of the Royal Canadian Mounted Police, said.

The suspects will appear in a Canadian court tomorrow for bail hearings.

In a statement, Amtrak said it was aware of the situation and is working with Canadian authorities during the ongoing investigation.

Check back for updates on this developing story.

NBC's Jon Dienst and Rich Esposito contributed to this report