The fiery explosion on a US-Canada bridge that shut down links with New York in the Niagara Falls area is being investigated as a "terrorist act," according to a media report.
Canada's Prime Minister Justin Trudeau told Parliament on Wednesday that the situation was "very serious".
"We're taking this extraordinarily seriously," he said before rushing out of the chamber.
Two people in the vehicle travelling from Canada were killed in the blast on the US side of the Rainbow Bridge, which leads to the iconic Niagara Falls, according to media reports quoting official sources.
A border official was injured.
The Federal Bureau of Investigation (FBI) said in a post on 'X' that the situation was "fluid" and it was investigating the incident.
Fox News said that according to its sources, the FBI was looking into it as "an attempted terrorist attack".
New York Governor Kathy Hochul said, "The New York State Police is actively working with the FBI Joint Terrorism Task Force to monitor all points of entry to New York."
All four bridges in the Niagara area were shut down and other crossings were put on "heightened alert status," the New York State Transportation Department said.
The explosion took place on the eve of Thanksgiving Day, a major holiday in the US, and amid heightened tensions over the Gaza conflict that has spawned high emotions and protests across the two American neighbours.
The annual Thanksgiving Day Parade in New York City attracts a crowd of about three million along its route and the city's Mayor Eric Adams said, "The NYPD (police department) and our team have been closely monitoring the situation."
The Niagara Frontier Transportation Authority said it was "increasing security system-wide" for cars and passengers coming into the Buffalo and Niagara Falls airports.
Fox News said that according to its sources, the vehicle carried explosives.
ABC News quoting its sources said that the vehicle, believed to be a Mercedes Benz, travelled at a high speed, hit a concrete barrier, careened into an area where cars waited for secondary inspection, burst into flames and exploded.
An eyewitness told NBC News, "The car was coming, flying back here, like over 100 miles an hour."
The car went up "like 30-40 feet high" after hitting a barrier and catching fire, the man said.