"The FBI Buffalo Field Office is investigating a vehicle explosion at the Rainbow Bridge," field office said in a post on X. "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."
New York Gov. Kathy Hochul posted on X that she had been briefed on the incident and said state agencies are "on site and ready to assist."
In a separate post, Hochul said she was headed to Buffalo to meet with law enforcement and emergency responders.
Officials have not said what caused the explosion.
Mark Poloncarz, the County Executive of Erie County, the county directly south of Niagara County, said in a post that all Western New York bridge crossings into Canada have been closed.