CROCKETT (CBS SF) — A conveyor system spanning five floors of the iconic C&H Sugar refinery in Crockett ignited into flames and heavy smoke Thursday, forcing employees to evacuate the building.

Assistant Contra Costa Fire Chief Terence Carey said firefighters responded to reports of a fire at the C&H Refinery nestled on the shores of the Carquinez Straits on Loring Ave. at about 8:46 a.m.

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Arriving crews discovered smoke billowing out of the five-story structure housing a massive conveyor belt on the backside of the building. Two additional alarms were called in as eventually 65 firefighters responded to fight the fire.

“It was very labor intensive to fight the fire,” Carey said. “We had wood burning. We had sugar burning. We had the conveyor assembly on fire.”

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Smoke filled the fifth, sixth and seventh floors, sending employees scurrying from the building. Fortunately, only the smoke was found on those floors as the fire remained inside the conveyor unit attached to the rear of the building.

Carey said there were no injuries to either firefighters or workers.

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The factory was closed after the blaze. Carey did not know when it would reopen. He said the fire remained under investigation.