BAY POINT, Calif. (AP) — The Latest on a fire threatening a natural gas pipeline in the San Francisco Bay Area (all times local):

8:15 a.m.

A fire is burning in an underground natural gas storage area in the San Francisco Bay Area and officials are working to empty the natural gas from a nearby Chevron pipeline after thousands of residents were evacuated.

Chevron spokesman Cary Wages told reporters Thursday that crews were purging gas from the pipeline in the city of Bay Point and would then inject nitrogen “which will extinguish the fire” still burning in the underground vault.

Contra Costa assistant fire chief Terence Carey said that a grass fire started Wednesday night near the pipeline and was quickly extinguished. A second fire was reported a short time later in the underground storage area.

Officials said about 4,000 people were evacuated from 1,400 homes within a half-mile (0.8 kilometer) radius of the pipeline.

Officials said Thursday they hoped to start letting people return home within hours, after the fire is extinguished.

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5:15 a.m.

A grass fire sparked by a power line failure was threatening a major Chevron natural gas pipeline junction Thursday, leading to the evacuation of about 1,400 homes.

Chevron officials say they learned of the blaze about 8 p.m. Wednesday, shut down the gas line and spent the night working to reduce pressure in it.

Authorities ordered evacuations at about 11 p.m. for all homes within half a mile (0.8 kilometers) of the site.

Fire officials advised residents not to be alarmed by a loud, shrieking noise that they described as being a “normal part of the risk-mitigation process” at the pipeline facility on Buchanan Road in Antioch.