RICHMOND (CBS SF) — A “suspicious” fire that destroyed the roof of an abandoned, boarded-up duplex in unincorporated north Richmond on Monday morning is under investigation, a fire captain said.

Crews from the Richmond Fire Department and the Contra Costa County Fire Protection District responded to a “suspicious” fire at 1621 Second St. at 6:15 a.m., Capt. George Laing of the Contra Costa County Fire Protection District said.

“The fire burned into the attic and the entire roof,” Laing said.

It took about 30-45 minutes for firefighters to put the main fire out, known as “knocking down the fire,” Laing said, and another few hours to put it out completely.

Laing estimated the damage as under $50,000. No one was hurt in the fire, he said.

“If you see people entering or loitering around vacant structures, be sure to call the authorities,” Laing said.

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