In Jan. 2012 dozens of cars crashed into each other along I-75 near Gainesville (Fla.), prompting some motorists to dial 911, even as the collisions continued.
The National Transportation Safety Board has two investigators at the site of the I-75 crash that killed 10, an official tells CBS News.
There is no specific threshold for investigating highway crashes, but the Board investigates "high consequence events and incidents." Ten people were killed and 18 others hospitalized in the multi-vehicle accident that occurred in low visibility early Sunday.
I-75 was reopened Monday morning as accident investigators tried to determine what caused the first crash that set off the fiery chain reaction that killed 10. The Florida Highway Patrol is leading the investigation.
CBS News correspondent Mark Strassmann reports it may turn into a criminal investigation.
Drivers were blinded by a combination of fog and smoke caused by a nearby brushfire - and that fire may have been set intentionally. State officials can find no natural cause, no natural explanation like a lightning strike, which could have started the brush fires.
The disaster scene ran for one mile along I-75, littered with the burned-out shells of up to 19 vehicles, including at least seven tractor-trailers. In zero-visibility conditions, a combination of smoke and fog, drivers headed into a deadly multi-car pileup.
"As we were coming through the prairie, it went from crystal clear visibility to nothing in 50 feet," crash survivor Bert Thomas told CBS News.
Visibility was so poor that when rescuers first arrived on the scene, they could locate victims only by listening for moans and screams.
Throughout the day, firefighters sprayed foam on smoldering wreckage and rescuers used machinery to pry victims from vehicles.
"It was a very traumatic situation and frightening situation to be out there on I-75. Hearing crashes, hearing explosions, hearing people scream," said Alachua County Sheriff spokesperson Sadie Darnell.
The interstate had been closed for a time before the accidents because of a mixture of fog and heavy smoke from a brush fire that may have been intentionally set. The decision to reopen it early Sunday will certainly be a focus of investigators, as will the question of how the fire may have started.
All lanes of I-75 reopened late Sunday, but authorities closed the highway again early Monday due to poor visibility caused by fog and smoke.
"It looked like the end of the world"
Steven R. Camps and some friends were driving home hours before dawn Sunday when they were suddenly drawn into the massive wreck.
"You could hear cars hitting each other. People were crying. People were screaming. It was crazy," the Gainesville man said hours later. "If I could give you an idea of what it looked like, I would say it looked like the end of the world."
The pileups happened around 3:45 a.m. Sunday on both sides of I-75. At least a dozen cars and six tractor-trailers were involved, and some burst into flames.
Hours later, twisted, burned-out vehicles were scattered across the pavement, with smoke still rising from the wreckage. Cars appeared to have smashed into the big rigs and, in one case, a motor home. Some cars were crushed beneath the heavier trucks.