US-Canada border closed at Rainbow Bridge after vehicle explodes ...

A speeding vehicle on the American side of a U.S.-Canada border crossing near Niagara Falls blew up Wednesday, killing two people and causing federal authorities to shut down four border checkpoints amid international concern.

The two people found dead were inside the vehicle that exploded, a law enforcement official told the Associated Press.

The FBI's field office in Buffalo said in a statement that it is investigating the explosion on the Rainbow Bridge, which connects the two countries across the Niagara River.

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

A witness, Mike Guenther, told WGRZ-TV that he saw a vehicle speeding toward the crossing from the U.S. side of the border when it swerved to avoid another car, crashed into a fence and exploded.

“All of a sudden he went up in the air and then it was a ball of fire like 30 or 40 feet high,” Guenther told the station. “I never saw anything like it.”

President Joe Biden and Attorney General Merrick Garland have been briefed on the explosion. Biden and his team are closely following developments, according to The White House.

The US Federal Aviation Administration has ordered a halt to international arriving and departing international flights at Buffalo Niagara International Airport at 3:07 p.m. Wednesday. The groundings are expected to be in effect until Friday afternoon, CNN reported.

The Canada Border Services Agency in a statement on X said it is "aware of an evolving situation at Rainbow Bridge."

"We are liaising with our U.S. counterparts on this matter. The FBI is leading on the ongoing investigation," the statement reads.

On Wednesday afternoon, New York Assemblymember Michael Novakhov wrote on Facebook "all border crossings between the U.S. and Canada remain closed and local government offices in the immediate area have been closed and evacuated."

New York Gov. Kathy Hochul said she had been briefed on the incident and was “closely monitoring the situation.”

What happened at the bridge crossing?

Photos and video taken by news organizations and posted on social media showed a security booth that had been singed by flames.

Aaron Ferguson, a public information officer for the city of Niagara Falls, told CNN: “We don’t really know too much – just that there was a vehicle trying to come into the US and they shut down both sides of the bridge."

American and Canadian airlines increase security, halt flights; Amtrak suspends routes

The Niagara Frontier Transportation Authority released a statement on Wednesday afternoon to inform travelers that while Buffalo and Niagara Falls Airports are "fully operational," there will be extra security measures.

"In the response to the incident that is unfolding at the Rainbow Bridge, the NFTA is increasing security system-wide," a statement from on X reads. "Cars coming into the Buffalo Airport will undergo security checks and travelers can expect additional screenings."

They advised travelers "to give themselves time for these extra precautions in addition to holiday travel."

What is the Rainbow Bridge?

The Niagara Falls International Rainbow Bridge is an arch bridge that connects the cities of Niagara Falls, New York, in the United States and Niagara Falls, Ontario, in Canada. The bridge can be crossed by car, on foot or by bicycle.

Contributing: Bart Jansen, Michael Collins, Dinah Pulver