NIAGARA FALLS, N.Y. (AP) — A border crossing between the U.S. and Canada has been closed after a vehicle exploded at a checkpoint on a bridge near Niagara Falls.

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

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

Further information wasn’t immediately available.

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

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.