Bentley may have experienced mechanical failure causing it to accelerate and plow into Canadian border, investigators claim as they reconstruct deadly chain of events that killed couple and sparked terror fears

Investigators trying to piece together events leading up to Wednesday's car crash on the US-Canada border are looking into whether the couple's $300,000 Bentley suffered a mechanical failure, the mayor of Niagara has said.

The pair - a 56-year-old New York businessman and his wife - were both killed in the devastating crash, which saw their car hurtle towards the border crossing at high speed, hit a curb and fly over a fence, landing at the border post and bursting into flames.

The victims are yet to be formally identified, in part owing to the inferno that engulfed the wreckage.

The crash sparked immediate fears of a terror attack, but by Wednesday evening the governor of New York, Kathy Hochul, reassured residents that there was no sign of terrorism. No explosives were found in the car.

'A search of the scene revealed no explosive materials, and no terrorism nexus was identified,' the FBI in Buffalo said in a statement.

'The matter has been turned over to the Niagara Falls Police Department as a traffic investigation.'

Robert Restaino, the mayor of Niagara, told The New York Times that vehicle malfunction was being investigated.

Their car, a 2022 Bentley Flying Spur, was almost entirely destroyed in the smash, with only the engine left intact.

Erin Bronner, a spokeswoman for the American arm of Bentley Motors, told the paper that the authorities had not yet contacted the automaker about the incident, so she did not have any information to disclose.

Restaino said the couple had originally been headed to a concert in Canada, and investigators believe it was a Kiss show that was called off after a band member's illness.

The pair stopped off at Seneca Niagara casino before approaching the border, a spokesman for the casino confirmed to DailyMail.com, but they were only inside for a few minutes, leading to speculation that they were there to change money.

Mike Guenther told Buffalo television station WGRZ-TV that he was walking near the bridge with his wife when the car, traveling 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. 

Video of the crash caught on security camera and posted to X by the U.S. Customs and Border Protection (CBP) agency showed the car traveling from the U.S. side at high speed, then hitting an object and flying into the air before crashing to the ground and exploding in flames.

Guenther said the vehicle, which he described as a luxury sedan, was 'fish-tailing' out of control before it crashed.

'He was swerving as he was going down this road here, fishtailing because he was going so fast,' he said.

'When he hit the fence there was a fire then, but then when he went up again he must have hit the building and there was a big noise and he just shot up in the air and you couldn't see nothing but smoke.

'We heard a big bang. I said there is no way that guy is going to stop, he is just going too fast.

'All of a sudden he went up in the air and then it was a ball of fire like 30-40 feet high, I have never seen anything like it. It was really incredible.'

Guenther described seeing 'car parts everywhere in pieces' after the horror smash. 

Guenther said fire trucks were first on the scene and within 10 minutes there were 'police everywhere'.

'We could see the fireball - that's all we could see, it was just smoke everywhere,' he added. 

'I don't think that person is going to survive, their car parts were everywhere.'