Three people have died after a fiery 14-vehicle crash on a major Ontario highway Tuesday evening.

The collision, which happened around 11:30 p.m., occurred south of Barrie, Ont., in the northbound lanes of Highway 400 north of Country Road 88, according to Ontario Provincial Police Sgt. Kerry Schmidt.

Police said at least two fuel tankers and a number of other transport trucks were involved. Schmidt said that “massive fireballs and massive explosions” reduced most of the vehicles to “shells” with “nothing left.”

“It is absolutely devastating,” Schmidt told CP24 on Wednesday morning. “There are cars everywhere. Twisted transport trucks, destroyed vehicles, metal that is unrecognizable.”

“As the fuel was flowing out of the trailers, which was split wide open, the fire was rolling down the highway,” Schmidt said. “People were running for their lives to not be encompassed by the moving fire.”

In a tweet on Thursday morning, police said the southbound lanes were reopened but the northbound lanes remained closed.

The cause of the crash is still under investigation, but Nirandran said the working theory is that a transport truck may have collided into the slowing traffic.

OPP Commissioner Vince Hawkes said it may be yet another example of “driver inattention.”

“There’s really no excuse for that transport truck to continue at the speeds that (it) did and impact the vehicles in the queue,” he told reporters.

“It’s a miracle that we don’t have about 25 bodies down there,” Hawkes added.

‘Very scary experience’

Sara Hlywka told CTV Barrie she was driving about 500 metres behind a tanker truck when it exploded. “If I didn’t break as hard as I did, I would have died,” she said.

Nicholas Marrs, who was driving with his girlfriend, said he saw a “flash of orange light” and “a transport truck and the whole highway was just in flames.”

“I don’t think I’m going to be driving on the highway for a while after that,” Marrs said. “It was a very scary experience.”

Kevin Gallant, fire chief for neighbouring town of Bradford-West Gwillimbury, said emergency crews were responding to a three-vehicle collision only a few hundred metres north on the highway, which created a slowdown when the pileup occurred.

Gallant said he saw two fuel tanker trucks and at least three transport trucks collided while he was on the scene of the first crash.

“When I looked to the south from the accident I was already on, all I saw was a big ball of fire," he said.

Dramatic video taken at the scene and posted online showed towering flames and thick plumes of smoke billowing into the night sky.

Luba Zariczny, 25, told CTV News Channel on Wednesday that she was driving home on Highway 400 to Mississauga, Ont. from her boyfriend’s house in Barrie when she saw the flames from the collision. She said she drove past the accident and pulled over to take a few videos of the massive fire.

“People were out of the cars. It looked like people had put their emergency lights on and probably ran from the scene. I saw a lot of vehicles just burnt up in flames, a fuel truck that was somewhat in the ditch as well, just completely engulfed,” she recalled.

Zariczny also described the heat she felt from the fire as she drove past the scene.

“It felt like there was a good 20 ovens just burning up,” she said. “It was that intense of heat.”

Loud explosions can be heard in the background of the video Zariczny shot.

The highway has been under construction for months. Schmidt said it sustained significant damage during the fire and will most likely need to be repaved and resurfaced.

Ontario Premier Kathleen Wynne called the event “a horrible, horrible tragedy” and said the province would be looking into what happened in the aftermath of the collision.

“We will be advised on whether there's more that could have been done to prevent such a crash," she said.

Prime Minister Justin Trudeau also expressed his condolences to the families of the victims in a tweet on Wednesday.

"Absolutely devastating news from southern Ontario. My thoughts are with those who lost a loved one in the horrific crash on Highway 400,” he wrote.

The investigation into what factors may have played a role in the crash is still in its early stages, but they’ll be looking at the possibility of mechanical deficiencies in the vehicles, what the environmental conditions were like at the time of the crash, and whether or not human factors such as inattention, impairment, distraction or aggressive driving contributed, Schmidt said.

The OPP held a press conference last week in order to highlight the dangers of accidents involving commercial transport trucks. More than 5,000 collisions, with 67 people killed, have involved transport trucks this year, police said. In the two years prior, there were a total of 13,668 crashes with commercial transport trucks, which killed 155 people.

There has been a 66 per cent decrease in the fatality rate from transport truck collisions between 1995 and 2014, the Ontario Trucking Association said last week. They also noted the fatality rate has gone down despite a 75 per cent increase in large truck vehicle registrations.

With files from CP24, CTV Toronto, CTV Barrie, Josh Dehaas and The Canadian Press