Firefighters on Thursday were investigating the cause of a morning fire that leveled an auto body shop on Route 4.

Fire crews responded at about 8:35 a.m. to a heavy blaze at Willie’s Auto Body at 457 Auburn Road, which is also Route 4. A fire official said that when they first arrived, they found the building engulfed by flames with the roof collapsing.

Police quickly shut down a section of Route 4 as fire crews from other departments arrived at the scene. Vehicles were detoured between Upper Street and Lower Street.

Everyone made it out of the building safely, officials said.

Flames and smoke were visible for miles and traffic along Route 4 slowed to a crawl as crews from multiple departments arrived at the scene. As the building burned, people as far away as Leeds and Greene reported they could see the smoke.

There were no immediate reports of injuries. The cause of the blaze was still being investigated later Thursday. It was expected the state fire marshal’s office would join the investigation.

The body shop has been in Turner for several decades. In 2005, it was saved from fire after a connected building went up in flames.

The disruptions on heavily traveled Route 4 come just a day after an accident in Auburn closed down traffic for the entire day.