Crews responded to reports of fire at a petroleum product refinery operated by Evergreen Oil Inc. at 6880 Smith Ave. at around 12:45 a.m., Alameda County Fire Department spokeswoman Aisha Knowles said.
Approximately 65 county firefighters as well as units from Fremont and Union City fire departments responded to the blaze, Knowles said. An aggressive attack by responding crews kept the flames contained to a single heater stack, Knowles said, and the blaze was declared fully controlled by about 2:15 a.m.
A preliminary investigation found that a non-hazardous transfer fluid caught fire within a heater stack structure, Knowles said.
No injuries were reported to firefighters or to the facility's employees. A shelter-in-place warning was not issued to surrounding neighborhoods during the emergency.
A plant manager told fire officials that the refinery, which operates 24-hours a day, remains fully operational this morning.
The cause was still under investigation.