FRESNO, Calif. (KFSN) --The fire sparked around 1 a.m. on Tuesday on Fresno Street, south of Clinton Avenue.
Fire officials say someone saw smoke billowing out of the building and called 911. Firefighters were able to stop the fire from spreading from the attic to other buildings.
The building was empty when firefighters got there. They say it appears to be an office space for sale. They also say it could've been a complete loss.
"The fire is under control. We're glad that whoever was driving by discovered it early. Otherwise, this whole building would probably have burned to the ground," said Batt. Chief Tony Escobedo.
Investigators say a burned mattress was found inside the apartment building. They believe someone homeless may have sparked the fire, but that is under investigation.