A vehicle has exploded on a bridge connecting the United States and Canada near Niagara Falls, the FBI has confirmed.

The explosion was on the Rainbow Bridge a day before the Thanksgiving holiday in the US.

Fox News is reporting the explosion as “an attempted terrorist attack” citing sources telling the broadcaster that explosives were in the vehicle at the time and two people who were in the car are dead.

Sources said there were no serious injuries, except to those who were in the car, reportedly two men.

A border officer has been injured, Fox News reports.

The FBI Joint Terrorism Task Force is working with New York State Police to “monitor all points of entry to New York”, State Governor Kathy Hochul said.

”The Rainbow Bridge is one of four border crossings connecting Ontario to western New York. The others are Lewiston, Whirlpool and Peace Bridge.”

The Niagara Falls Bridge Commission reports all four crossings are closed.

The vehicle was trying to enter the US at the time of the explosion.

The moment the vehicle exploded was captured by surveillance cameras in the area, CNN reports.

The FBI says it is coordinating with its local, state and federal law enforcement partners in the investigation.

Photos and video taken by news organisations and posted on social media showed a security booth singed by flames.

Law enforcement personnel block off the entrance to the Rainbow Bridge. Photo / AP 

Mike Guenther from Ontario was walking with his wife near the Rainbow Bridge when he says they saw a car driving at high speed. It swerved around a car in front of it and then slammed into a fence.

”He went up in the air and there was a ball of fire like 30 or 40 feet [9-12m] high,” Guenther said.

“He was flying, like over a hundred miles [160km] an hour,” Guenther told local media.

The explosion rocked the Rainbow Bridge connecting Canada and the United States. 

Border police were present at the time of the crash and within 10 minutes more law enforcement officers had swarmed the area.

”All of a sudden there was just police everywhere.”

The vehicle was fishtailing and out of control just before the explosion, Guenther said.

”I said there’s no way that guy’s going to stop, there’s no way he can stop, he’s just going too fast.”

Ivan Vitalii, a Ukrainian visiting Niagara Falls, told the Niagara Gazette that he and a friend were near the bridge when they “heard something smash”.

“We saw fire and big, black smoke,” he told the paper.

The Niagara Frontier Transportation Authority posted on X that all cars arriving at the Buffalo Airport would undergo security checks. The authority said travellers should also expect increased screenings.

Canadian Prime Minister Justin Trudeau has been briefed, his office said.

Canadian Public Safety Minister Dominic LeBlanc said the government is taking the explosion “extremely seriously”.

LeBlanc is receiving regular updates from US authorities, Royal Canadian Mounted Police, and border service agencies, CNN reports.

The Buffalo Niagara International Airport has closed to both international arriving and departing flights, according to the US Federal Aviation Administration.

- AP Additional reporting