A large fire at Chevron Corp.'s (CVX) Richmond, Calif., refinery has been extinguished, even as traders, bracing for a lengthy outage, were bidding up regional fuel prices.

The Richmond Police Department dispatcher said the fire was "completely out" shortly before 10 a.m. EDT. Chevron spokesman Lloyd Avram said the main fire was extinguished, and safety officials were allowing "a small controlled burn," a safety measure intended to reduce the escape of pollutants into the atmosphere. The company didn't provide an update on production at the 245,000-barrel-a-day facility, which is the largest in the San Francisco Bay area and accounts for nearly 10% of the refining capacity in the U.S. West Coast.

Paul Sankey, an analyst with Deutsche Bank, wrote Tuesday the refinery is likely to be out for several months, and could translate into a 20-cent-per-gallon bump in California gasoline prices, already some of the highest in the country. The premium traders paid for spot Los Angeles Carbob gasoline delivered in August versus Nymex RBOB gasoline jumped 25 cents a gallon Tuesday, as concerns about near-term deliveries from the Richmond facility spread.

"Supply was relatively tight to begin with and the current high premiums may be with us for some time," a trader of West Coast crude said.

Tuesday, regular unleaded gasoline in the state averaged $3.859 per gallon at the pump, above the national average of $3.634 per gallon, according to AAA.

"For now, it looks like a lot of Golden State people will see $4 [per gallon] pump prices this month," said Oil Price Information Service analyst Tom Kloza. Mr. Kloza added California can get by with this outage, but if another plant has an event, the jump in prices could be "spectacular."

The fire broke out around 6:15 p.m. local time Monday at a crude-distillation unit, which was also leaking petroleum, Chevron said in a filing with the California Emergency Management Agency, adding there were no fatalities. Authorities had residents shelter in place to avoid noxious fumes, but the order was lifted by Contra Costa County Health Services at 11:31 p.m. local time Monday. Chevron said all its employees and contractors have been safely accounted for; three employees suffered minor injuries and were treated at the refinery, the company said.

The Doctors Medical Center in San Pablo, Calif. said between 7 p.m. Monday and 8 a.m. Tuesday local time, it admitted 181 people who complained of respiratory problems and eye irritation. "Most patients were released after being seen," the center said.

Chevron shut No. 4 CDU, where the fire broke out, but Chevron spokesman Brent Tippen said other parts of the refinery were running. The fire caused the refinery to emit large clouds of sulfuric acid and nitrogen dioxide, the company said in a filing.

Mr. Tippen said the company is working to repair the affected equipment, but declined to say how long that is expected to take.

"We cannot speculate on price, supply or production impacts," Mr. Tippen wrote in an email.

He said the company is investigating the cause of the fire.

"We will not speculate on the cause of this incident," Chevron said in a prepared statement. "Our priority right now is containing the fire and protecting the health and safety of our employees and community."

The Richmond refinery runs crude from Alaska and the Middle East, a company spokesman said. Its effect on global oil markets "will depend on the length of the closure. If long, then of course it backs out more crude," spilling unexpected supplies into the prompt market and driving down spot premiums, weakening the market structure, a Singapore crude-oil trader said.

On Aug. 1, Chevron had reported an incident at the same refinery, when it reported a flaring event to California state environmental regulators after a compressor failure caused a release of sulfur dioxide and hydrogen sulfide. Chevron said at the time the refinery would continue to supply products to its customers.

The Richmond refinery has long been a matter of contention for Bay Area environmental groups. In 2008, local groups sued to halt a planned upgrade to the refinery that would have allowed it to operate more efficiently and to process new types of crude, arguing the environmental review for the project was incomplete.

A California Superior Court judge and later a Court of Appeals judge agreed the review didn't provide all the information required by California laws and halted the planned $1 billion upgrade.

--Angel Gonzalez, Gurdeep Singh and Tom Fowler contributed to this article.

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