The Buffalo Niagara International Airport in New York is "open and fully operational" after being shut down briefly following a vehicle explosion at the Rainbow Bridge at US-Canada border on Wednesday afternoon, CTV News reported.

The US Federal Aviation Administration had reported that a closure was in effect at the airport and that flights in and out of the airport were grounded.

However, airport officials never reported that the airport had closed, and stated in a pair of posts on X (formerly Twitter) that the airport was "open and fully operational".

"In response to the incident that is unfolding at the Rainbow Bridge, the NFTA is increasing security system-wide," the Niagara Frontier Transportation Authority wrote in an update on X on Wednesday afternoon, adding that cars coming into the Buffalo Airport will undergo security checks and travellers can expect additional screenings, CTV News reported.

"We advise travellers to give themselves time for these extra precautions in addition to holiday travel," it added.

Notably, while the Canadian government officials had been operating under the assumption that the explosion was terror-related, CTV News reported citing national security sources, the US officials have said that there is "no indication of a terrorist attack" at this point of time.

At least two people were killed after a 'vehicle explosion' at the US-Canada border crossing near Niagara Falls in the afternoon hours on Wednesday.

Four US-Canada border crossings in the region have been closed as investigators respond to the situation, it said.

A senior US law enforcement official told CBS News that the car was coming from the US side. It hit the customs station and the vehicle was charred. It is not yet known why the car exploded.

A senior White House official told reporters that the White House is closely monitoring the situation and matter is being investigated.

"The White House is closely monitoring the situation, law enforcement is on scene and investigating," the senior White House official said.

Meanwhile, the FBI Buffalo Field Office in a statement that the incident is being investigated in coordination with local, state and federal law enforcement partners.

"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," it posted on X (formerly Twitter).

The Rainbow Bridge, which links Niagara Falls, Ontario, Canada, and Niagara Falls, New York, is a well-liked tourist destination.

The Lewiston-Queenston Bridge, the Whirlpool Rapids Bridge, and the Peace Bridge are the other border crossings in the area.

The Rainbow Bridge crossing connecting the US and Canada near Niagara Falls has been shut as the federal authorities in Buffalo, New York, have said that an investigation is underway.