Cape Breton Regional Police are investigating a suspicious fire that destroyed hundreds of vehicles at a junkyard Tuesday evening.

Fire crews were called to the salvage yard off Sydport Road in Coxheath, N.S., around 7 p.m. When they arrived, a large pile of old vehicles was engulfed in flames.

“Many of them still had gas and other fluids inside so they were exploding left, right and centre. You could hear the ‘pops’ like fireworks from the scene,” said CTV Atlantic’s Ryan MacDonald, who witnessed the fire from the highway. “The smoke clouds billowing up into the sky, you could see them from kilometres away.”

Roughly 50 firefighters from seven volunteer fire departments battled the blaze for several hours.

Police were also called to the scene to assist with traffic control.

No one was injured but an estimated 300 to 500 cars were destroyed in the fire.

"There's a lot of compressed gases and different safety items that are in vehicles, and when they become heated, even bumpers, they can discharge," said Deputy Chief of Cape Breton Regional Fire, Chris March.

Police remain on scene and are working with the fire marshall’s office to determine a cause.

"It's really tough to say,” said March. “(Tuesday) was a mild day. There was a lot of moving of vehicles.  If there was some residual fuel present, the placing of vehicles on top of one another, it could have created a spark."

Meanwhile, municipal zoning officials are working with the Nova Scotia Environment Department to determine whether the site was properly licensed.

"The owner can be fined, as a zoning violation," said Malcolm Gillis, Cape Breton Regional Municipality’s director of planning. “Obviously, what burns in metal are the fluids that are in it, and if you're in the salvage business, according to Nova Scotia Environment, the fluids are supposed to be removed." 

The scrapyard owner recently applied for industrial approval under the province’s environment department, but that application was rejected less than two weeks ago.

“There were a few technical items that had to be addressed and he apparently was going to try to reapply," said Environment Minister Margaret Miller.

The scrapyard owner was also seeking a municipal zoning amendment with hopes of expanding.

Anyone with information about the incident is asked to contact police or Crime Stoppers.

With files from CTV Atlantic’s Ryan MacDonald.