FRESNO, Calif. (KFSN) -- Firefighters are investigating what sparked a blaze at an empty office building in central Fresno.
An off-duty fire investigator driving by the area saw the fire and called it in shortly before 4 am.
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Crews arrived to find fire coming from one side of the building, but they were able to get it out quickly.
Firefighters then searched the building but found no one inside.
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They say this building has caught fire several times before Wednesday's incident.
No other buildings were involved in the blaze.