A truck fire that sent four people to hospital over the weekend may have been caused by an explosive.

Neighbours heard people screaming and saw a burst of flames on Saturday night. A truck carrying four people caught on fire on Gallagher Avenue. The driver crashed into a fire hydrant in a residential neighbourhood.

But it appears the collision may not be the cause of the blaze that sent the four occupants to hospital with serious burns. Nick Chastellaine said his girlfriend, cousin and friend were in the truck.

"My cousin is traumatized and I believe my girlfriend is going to be too," said Chastellaine.

Chastellaine said his girlfriend found a backpack on the hood of another car in a nearby convenience store parking lot. He said she took the backpack inside the truck, they began to drive away, and

that's when he said disaster struck, and that some sort of explosive was inside the bag.

"She went and grabbed it and they drove around the corner, I guess she went to go look inside and it just engulfed in flames inside, it wasn't no collision it was a fire bomb," said Chastellaine.

Police won't say what caused the fire and won't say whether a backpack was involved. Police did acknowledge that this is not a case about a car hitting a fire hydrant.

"This is now being investigated by the Major Crimes Unit so there are obviously complexities to this case, it goes without saying it’s not just a motor vehicle collision," said Const. Rob Carver.

Emergency crews showed up on scene within minutes and extinguished the blaze and assisted the victims. Neighbours tell CTV News one of the men from the truck was on the street and was on fire and had to rip off his clothing.