Updated at 4 p.m. Aug. 4 with additional details.
An investigation is underway to determine what caused a fire Saturday morning behind a seafood restaurant in Lemon Grove.
Flames were reported coming from the roof of on Federal Boulevard near Broadway at 3:15 a.m.
Heartland Fire & Rescue crews from Lemon Grove and La Mesa, assisted by units from San Diego Fire, arrived to find a fire burning on the outside of the back of the building.
The flames had also spread to the attic, so firefighters cut a hole in the roof for ventilation. Officials said the sprinkler system in the attic helped firefighters quickly contain the fire and keep the flames from spreading to adjacent units.
The interior and exterior of the building was damaged, but no injuries were reported. Prior to fire department arrival, San Diego Sheriff’s Department evacuated three people who were sleeping in the upstairs loft of the restaurant.
Officials said San Diego Sheriff’s Bomb/Arson Unit is investigating the cause of the fire because it was "incendiary in nature."