The FBI says a deadly car crash and explosion at the Rainbow Bridge border crossing between New York state and Ontario shows no sign of terrorist involvement and there were no explosive materials at the scene, and the case has been turned over to the Niagara Falls Police Department as a traffic investigation.

Details of what led to the crash remain scarce, with security camera video released by the U.S. government showing the car speeding through an intersection, hitting a low median and flying through the air into a line of vehicle checkpoint booths on the American side of the crossing.

Federal Public Safety Minister Dominic LeBlanc says both Canada and the U.S. are taking the "violent circumstance" very seriously, but stresses it is "simply not responsible" to speculate on what caused the incident without more accurate information.

The crash and subsequent explosion prompted the closure of three other area border crossings between Ontario and western New York for hours, along with additional passenger screenings and vehicle security checks at the Buffalo-Niagara International Airport.