KNOXVILLE, Tenn. (WATE) — Knoxville Fire Department said investigators have determined the explosion that led to the fire at a South Knoxville transmission shop in the 1200 block of Maryville Pike started near a heating device that is similar to a water heater.

KFD says the fire appears to be accidental in nature, and the lone person injured, owner Dave Johnson, has been released from the hospital. At least 18 vehicles parked at the business were damaged.

A large plume of black smoke could be seen from most areas of the city on Monday when the fire began. Fire officials said once that smoke cleared and hot spots were extinguished, investigators were able to examine the damaged structure.

It was determined the fire at Dave’s Wholesale Transmission started near or around a device used for heating that utilizes a gas-fed flame to heat a cylinder of reclaimed or recycled oil, the department said.

STAY INFORMED: Download: the WATE 6 On Your Side News and Weather Apps

Employees at work when the fire ignited on Monday told officials that the area of which the heating device is where the fire started. They also said they attempted to use fire extinguishers to fight the flames while contacting emergency services.