Indianapolis, IN – Investigators think a natural gas leak caused an explosion and fire that damaged a south side car wash Friday night.

The explosion was heard at Brad’s Car Wash on Shelby Street shortly after 9 p.m. More than a dozen units from Indianapolis and Greenwood fire departments responded to find heavy fire and smoke when they arrived.

Workers told investigators they noticed a rotten egg smell in the building over the past few days that initially dissipated, but then returned Friday before the explosion. According to Indianapolis Fire Department Battalion Chief Rita Reith, the employees said they did nothing to investigate the source of the odor.

Investigators determined the explosion happened above the main office and break room and lifted the roof several feet. Interior walls were damaged and several of the exterior windows were also blown out.

Reith said investigators are “confident” natural gas caused the explosion, but they have not traced to source of the leak or the ignition source.

Damage is estimated at $3.5 million.

Mechanical engineers will be the next to investigate.

Citizens Energy found no leaks in their lines into the building and believe the leak came from inside the car wash, leaving no further hazard to the public.

Investigators found debris from the explosion up to 150 yards from the car wash in all directions. Two businesses in a nearby strip mall – Michael’s and Hobby Lobby – also sustained damage from the blast.