REDDING, Calif. -

Firefighters responded to a commercial structure fire Saturday morning at 8788 Airport Road in Redding.

The fire was reported around 11:30 a.m. at Northstate Mechanical Services.  People at a neighboring business heard a loud pop sound, lost electricity and called 911.  Smoke was seen coming from the business.

Firefighters found a fire burning inside the wall. Damage was limited to the one wall, and smoke damage to the interior of the building.

Units from Redding, Anderson, Shasta County and CAL FIRE all responded.  

Investigators said the cause was likely electrical, but the investigation will continue.