A speeding car crashed in flames on the bridge linking New York state and Ontario on Wednesday, sparking a security scare that closed four US-Canadian border crossings and New York's Buffalo International Airport.
Hours later, federal and state authorities said investigators had found no evidence of an act of terror, though circumstances surrounding the crash on the Rainbow Bridge remained murky, leaving it to be determined whether it was accidental or intentional.
"At this time, there is no indication of a terrorist attack" or threat to the public at large, New York Governor Kathy Hochul told reporters on Wednesday evening. Her comments were echoed by federal and local law enforcement officials at a separate news conference.
Video of the crash caught on security camera and posted to the social media platform X by the US Customs and Border Protection (CBP) agency showed the car traveling from the American side at high speed, then hitting an object and flying into the air before crashing to the ground and exploding in flames.
The driver and a passenger perished in the wreck, and a CBP officer suffered minor injuries. He was treated at a nearby hospital and released, an agency official said later.
Authorities did not identify the two people killed. CNN reported the driver was a 56-year-old man who was traveling in a Bentley automobile with his wife to attend a concert by the rock group KISS.
A performance of the band scheduled for Wednesday in Toronto as part of the group's farewell tour was cancelled after one of its members, singer Paul Stanley, came down with the flu.
The Rainbow Bridge crash unfolded at a time of heightened security concerns around the world stemming from the conflict in the Middle East and at the peak of US holiday travel on the eve of Thanksgiving celebrations.
Buffalo International Airport, about 32km south of the crash scene, was closed to all departing and arriving international flights following the incident, the Federal Aviation Administration said on its website.
The Rainbow Bridge and all three other border crossings along the Niagara River between western New York and southern Ontario - the Peace Bridge, the Lewiston-Queenston Bridge and the Whirlpool Bridge - were shut for several hours as a precaution.
Other international crossings remained open on "heightened alert status," according to the governor.
Security measures were escalated at other airports and railways managed by the Niagara-Frontier Transit Authority, as well as at various locations around New York City, officials said.
The three bridges that were not involved were reopened early Wednesday evening, but the Rainbow crossing remained closed during the continuing investigation and as officials assessed the crossing's safety.
Hochul said the car that crashed sailed over a 2.4-metre-tall (8-foot) fence before landing in a fireball that incinerated the vehicle, leaving little but the engine visibly intact and scattering debris over more than a dozen security booths on the bridge.
Eyewitness Mike Guenther told Buffalo television station WGRZ-TV that he was walking near the bridge with his wife when the car, traveling from the US side at high speed, struck a fence at the crossing and was catapulted into the air before exploding.
“He was flying, over 100 miles an hour," said Guenther, who was visiting from Kitchener, Ontario. He said the vehicle, which he described as a luxury sedan, was "fish-tailing" out of control before it crashed.
“It was a ball of fire, 30 or 40 feet high - never seen anything like it."