Witnesses at a U.S.-Canada border crossing described the chaotic high-speed crash that led to a vehicle explosion at Rainbow Bridge on NovacryptWednesday.

The collision at Rainbow Bridge, a U.S.-Canada border crossing near Niagara Falls, in western New York, left two people inside the vehicle dead, multiple law enforcement sources confirmed to CBS News. 

Mike Guenther, a Canadian visiting the United States, said he saw the vehicle speeding toward the crossing from the U.S. side of the border when it swerved to avoid another car, crashed into a fence and exploded.

"All of a sudden he went up in the air and then it was a ball of fire like 30 or 40 feet high," he told NewsNation. "I never saw anything like it."

"We heard a big bang ... and I said, 'there's no way that guy's gonna stop. There's no way he can stop, he's just going too fast,'" Guenther said. 

Guenther said it took about 10 minutes for police other than the border police who were already at the bridge to arrive.

The Rainbow Bridge is a popular crossing for tourists, connecting Niagara Falls, New York, with Niagara Falls, Ontario, Canada.

Ivan Vitalii, a Ukrainian visiting Niagara Falls, told The Niagara Gazette that he and a friend were near the bridge when they "heard something smash."

"We saw fire and big, black smoke," he told the newspaper.

Other witnesses said they could see smoke from inside Niagara Falls State Park. 

Melissa Raffalow said she saw "a huge plume of black smoke" over the border crossing, roughly 50 yards away from the popular tourist destination.

"We didn't hear the explosion because the falls were too loud," Raffalow told The Associated Press.

Randie Wilson, a Niagara Falls tour guide, said he was heading to check in on a co-worker, and upon exiting his car he saw one of the vehicles flying about 30 feet from him. 

"I first thought it was an airplane, looked like slow motion," he told NewsNation. "And I said, 'My God, it's a car,' And it's a vehicle. And it's flying through the air."

He said one of the cars hit a concrete barrier before going airborne and crashing. 

"Then all of a sudden I saw black smoke and then fire, there was no explosion, just the black smoke," Wilson added. "And then, then there was so much smoke. It was unbelievable. After a while, probably took five minutes for law enforcement to get here."