Canadian security forces thwarted a plot to blow up a rail line between Canada and the United States and will announce arrests on Monday afternoon, police and intelligence agencies said.

U.S. security and law enforcement sources also said the suspects had sought to attack the railroad between Toronto and New York City. Canadian media said two men had been arrested after raids in Toronto and Montreal, Canada’s two biggest cities.

Canadian police are holding a briefing about a “national security criminal investigation” at 3:30 p.m. ET (1930 GMT). . .