RICHMOND (CBS SF) — The Bay Area Air Quality Management District dispatched inspectors to the Chevron refinery in Richmond Thursday morning after they received at least two complaints about flaring.

The flaring at Chevron Richmond Refinery, listed at 525 Castro St., started around 7:30 a.m., according to district spokesman Tom Flannigan.

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It was continuous, initially, but Flannigan said it had become intermittent by late morning.

It’s not yet clear what events led to the flaring, but district personnel will be working with the refinery to determine exactly what occurred and how.

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“As a part of the flare minimization rule, the refinery will have to take steps to prevent flares like this from happening again,” Flannigan said. “If a certain failure occurred, they’ll have to come up with a plan to prevent it in the future.”

It’s also not yet clear exactly what chemicals were involved in Thursday morning’s flaring event, but the air district is taking readings in the area and will issue notices of violation if the any regulatory violations occurred.

The refinery issued a statement on Twitter around 8:45 a.m.  calling the flaring process a “highly regulated” safety measure that is monitored by the air district.

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Flaring from the Chevron Richmond refinery exceeded a state limit on New Year’s Eve, according to the Bay Area Air Quality Management District. While the flaring exceeded state limits, it did not exceed air district or federal limits.