Hours after an earthquake measuring 4.5-magnitude struck San Francisco Bay area on Tuesday,  fires at two ethanol tanks were reported in NuStar Energy facility in California, the fire department said.

The Cal Fire Santa Clara Unit said firefighters from the Crockett-Carquinez Fire Protection District and over 10 assisting agencies are working to containing the fire at the petroleum tanker in Contra Costa county.

While it was earlier reported that three tankers had caught fire, the fire unit clarified later saying that two tankers were involved. An evacuation notice was issued by the Contra Costa County Sherriff's Office due to release of hazardous materials from the fire.

Reports suggest around 42 fire units in the Bay area have responded to the fire. Around five engines with "Specialized resources" from Chevron, Shell, Marathon, Phillip and Corteva were working under the unified command to control the issue, Costa County Fire Department spokesman Steve Hill was quoted as saying by the LA Times.

No injuries have been reported yet and the officials are "less concerned" about the threat of spreading to nearby tanks.

One of the tanks likely to be involved in the fire contains around 167,000 gallons of ethanol according to the fire department. The two tanks contain about 250,000 gallons of ethanol, Hill said.

More than 200 firefighters are involved in the de-escalation of the fire. Foam and water are being used to attack the flames and cool the adjacent tanks.

NuStar refinery fire
Petrol-Chemical Mutual Aid Organization (PMAO) resources, working for the NuStar Incident Command covered the remaining flammable material with foam in an attempt to prevent additional flare-ups.Twitter/ContraCostaFire

A statement issued by NuStar said the two impacted tanks had less than 1 per cent of the capacity.

While no details about the origin of the fire have been officially released, multiple reports suggested that an earthquake measuring 4.5 that struck the San Francisco Bay area resulted in the fire.

The tremors were felt in Oakland and San Jose as well and was reported to not have caused any major structural damages.

The recent tremors came days ahead of the 30th anniversary of the 6.9-magnitude Loma Prieta earthquake that was responsible for 63 deaths and 3,757 injuries in 1989, Northern California.