The fire was reported at 3:35 p.m. at Seeo, a company located at 3906 Trust Way, Hayward fire Capt. Thor Poulsen said.
Firefighters arrived to find heavy smoke and fire at the company's lab, and eventually found the source of the blaze -- a bucket with the chemical hexane in it that had caught fire, Poulsen said.
The chemical is extremely flammable and burns with a nearly invisible flame, he said, adding that investigators do not know why the material caught fire.
The blaze was extinguished at 3:56 p.m. and was contained to the laboratory, according to Poulsen.
About 25 employees at the company were safely evacuated from the building and no injuries were reported to any firefighters or civilians, Poulsen said.
The fire department's hazardous materials coordinator and fire marshal were at the company late Friday afternoon to try to determine the cause of the fire, which caused about $1,000 in damage to the lab, Poulsen said.