Dozens of children and some adults have been taken to hospital with minor injuries after two school buses burst into flames when they were involved in a three-vehicle crash in Saint-Eustache, Que., 40 kilometres northwest of downtown Montreal.

The buses were carrying more than 50 summer campers between the ages of seven and 12 on their way to Oka from their summer camp in Brossard, Que., on Montreal's South Shore, when the crash occurred around 10 a.m. ET Tuesday.

Police said a vehicle in front of the buses came to a sudden stop, triggering the collision and the resulting fires.

Francis Marleau was working at a car dealership just off Highway 640 when he heard the crash. He said he watched as thick, black smoke billowed from the buses, and he immediately sprang to action.

Marleau, along with employees from the dealership and two neighbouring ones, ran to the scene with ladders and stools, helping children still inside the burning buses get out. Some were carried out in rescuers' arms.

"I didn't want them walking," on the highway, Marleau said. "There was still traffic passing."

Police say the buses collided after the vehicle in front of them made a sudden stop on Highway 640 West. 0:09

The children were brought into one of the car dealerships and provided with water while they waited for help to arrive. Marleau said none of the children looked hurt, although many seemed shaken by the accident.

"The day camp monitors really did a great job," Marleau said.

"They controlled everything, from A to Z. I think they're really well-trained."

Charred ruins

No one was seriously hurt, but a total of 69 people were taken to the local hospital as a precaution and to be treated for minor injuries, according to Myriam Sabourin, a spokesperson for the regional health authority, the CIUSSS des Laurentides.

Sabourin said the hospital is treating the accident as a "code orange," meaning all its teams have been mobilized to evaluate those involved.

While they wait to be checked out, the children have been given food and water, and there are mental health workers with them, to help the children process what happened, Sabourin said.

The municipality of Brossard said in a statement that the local community service centre will be offering psychological support for children, parents and camp staff.

It said activities at the camp will go ahead as scheduled tomorrow.

Provincial police are investigating the crash which, according to a spokesperson, may have been caused by distraction. (Ryan Remiorz/The Canadian Press )

André Southière, a supervisor with the busline Réseau de Transport de Longueuil, said both bus drivers were experienced drivers.

"This is the first major accident that I've seen since I started with the company," Southière said.

Neither of the drivers showed signs of injury, he said, but are being checked out nonetheless.

The buses are charred ruins and beyond repair.

A spokesperson for Quebec provincial police, who are investigating the crash, said distraction may have been the cause of the collision.

The vehicles have been removed from the scene, and the highway has been reopened to traffic.