The car crashed into a checkpoint on the Rainbow Bridge in Niagara Falls at high speed and caught on fire, according to Sky's US partner NBC News.

Senior law enforcement officials said there was no indication that a bomb was inside.

Two casualties have been reported - and the authorities are trying to determine whether the incident was intentional.

The Rainbow Bridge, which connects the two countries across the Niagara River, and three other border crossings in the area have been shut.

Canada's public safety minister Dominic LeBlanc said it was too soon to say if the crash was a deliberate act.

Images and video purportedly from the border control scene showed a blaze and debris on the ground.

A security booth was singed by flames.

The vehicle was heading into the US from Canada, the Erie County Sheriff's Office said.

The incident comes a day before Thanksgiving, a US public holiday when millions of Americans visit friends and family. Many people will have already started their journeys.

On the roads, the American Automobile Association expects 55.4 million travellers to head 50 miles or more away from home from Wednesday to Sunday, up 2.3% over last year.

The Niagara Frontier Transportation Authority said it would be increasing security system-wide.

Travellers at the Buffalo Niagara International Airport should expect additional screenings and vehicles coming into the airport will undergo security checks, the agency said.

"The Buffalo and Niagara Falls Airports are fully operational. We advise travelers to give themselves time for these extra precautions in addition to holiday travel," the agency said in a post on X.

The Niagara Falls Bridge Commission reports all four border crossings connecting Ontario in Canada to western New York have been closed. The others are Lewiston, Whirlpool and Peace Bridges.

The governor of New York state also confirmed there had been an incident on the bridge - and authorities are closely monitoring the situation.

In a statement, Governor Kathy Hochul said: "I've been briefed on the incident on the Rainbow Bridge in Niagara Falls and we are closely monitoring the situation.

"State agencies are on site and ready to assist."

In a statement on X, the FBI in Buffalo wrote: "The FBI Buffalo field office is investigating a vehicle explosion at the Rainbow Bridge, a border crossing between the US and Canada in Niagara Falls.

"The FBI is coordinating with our local, state and federal law enforcement partners in this investigation. As this situation is very fluid, that's all we can say at this time."

Ontario Premier Doug Ford wrote on X: "I've been made aware of the situation unfolding on the Rainbow Bridge in Niagara Falls. Our provincial law enforcement is actively engaged in assessing the situation.

"They are working with local law enforcement and are providing support as required."