DENVER (KDVR) — An investigation is underway after four semi-tractors caught on fire and exploded at a truck stop in Weld County on Wednesday night.

Around 9:50 p.m. on Wednesday, Mountain View Fire Rescue said a caller reported a commercial vehicle fire to Weld County Dispatch. The fire was reportedly at a truck stop along Colorado Highway 119, just west of Interstate 25.

Once crews arrived on the scene, the fire rescue said they found four semi-tractors on fire, and three of them were fully engulfed in flames.

Battalion 201 responded first, and the fire rescue said they called in Engine 203, Tender 3441, Engine 3404 and Battalion 3460 from Frederick Firestone Fire.

The fire rescue said there were explosions from the fuel tanks and tires, and firefighters spent 20 minutes getting the fire under control. About 40 minutes after the fire was reported, crews were about to put the fire out. They spent the next hour mopping up any hotspots.

No injuries were reported, and the MVFR fire marshal, a deputy fire marshal and the Weld County Sheriff’s Office are now investigating. At this time, the cause of the fire is unclear.