An explosion at a bridge that links the United States and Canada near Niagara Falls has led to the closing of all nearby border crossings between the two countries, according to multiple reports.

The explosion reportedly occurred when a car coming from Canada was attempting to enter the U.S. via the Rainbow Bridge. The car passed the first checkpoint and was heading to a second when the explosion occurred. The two occupants in the vehicle are dead, according to CNN, citing an unnamed law enforcement source.

The exact cause of the explosion is currently unknown. However, the FBI Buffalo Field Office and local, state and federal authorities are investigating the incident. The FBI Joint Terrorism Task Force is also at the scene collaborating with New York State Police, Gov. Kathy Hochul (D) said.

“I’ve been briefed on the incident on the Rainbow Bridge in Niagara Falls and we are closely monitoring the situation,” Hochul added. “State agencies are on site and ready to assist.”

“As this situation is very fluid, that’s all we can say at this time,” the FBI Buffalo Field Office said in a post on X, the site formerly known as Twitter.

The Niagara Frontier Transportation Authority, the entity responsible for the public transportation system as well as the Niagara Falls International Airport and Buffalo Niagara International Airport, said it is increasing its security “system-wide.”

“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 NFTA said.

This is a developing story. Please check back for updates.