Thick black smoke could be seen in Guelph on Monday afternoon after an explosion rocked a 5 ton truck at a job site.

Four men were doing work on a storage facility on Elizabeth St. Three of them were on the building’s roof and one was in the truck when the explosion happened – no one was injured.

Clint Budnick was one of the workers and says panic set in immediately.

“There was a big bang and lots of smoke and we ran to the edge to make sure we got our fourth guy out who was inside the truck when it blew up,” says Budnick.

The workers told CTV News a generator in the back of the truck caused the fire. Guelph Fire officials are still investigating.

“When our crews arrived they did gain access to the rear of the building and they did find a couple of vehicles that were on fire,” says Deputy Fire Chief John Osborne, Guelph Fire Department.

Flames spread to a second truck – leaving nearly thirty fire fighters to put out the blaze.

None of the storage units were damaged. There is no word on damage costs for the trucks that caught fire.

With reporting by Victoria Levy