Reporting from Seattle — Four workers were killed and three others critically burned Friday when an explosion tore through a Tesoro oil refinery in Anacortes, Wash., the latest in a series of troubling refinery accidents that have touched off a nationwide inquiry.
"We're very concerned," said Daniel Horowitz, spokesman for the U.S. Chemical Safety Board, which is dispatching an investigative team to the scene of the accident 70 miles north of Seattle.
"Our agency investigates only the most serious oil and chemical accidents across the country. We have 18 open cases, including this one, and nearly half of them are at oil refineries," he said.
Tesoro, which was fined last year by the Washington Department of Labor and Industries for a series of safety and health violations at the plant, said the cause of the early-morning explosion and fire was still under investigation.
The refinery, part of a large complex in upper Puget Sound, processes about 120,000 barrels of oil a day into gasoline, jet fuel and diesel for markets in Washington and Oregon. It also sells liquefied petroleum gas and asphalt.
Refinery officials said the accident happened around 12:30 a.m. Friday during the dangerous process of restarting the unit's naphtha unit after maintenance. Naphtha is a volatile hydrocarbon mixture that is often used as feedstock for producing high-octane gasoline.
The explosion shook the entire area around the refinery complex and sent flames towering more than 100 feet in the air, according to witnesses.
"My whole house shook like an earthquake. The windows rattled, and I looked over at the refineries, and you could see big flames coming out," said Lisa Wooding, who lives about a mile away. "There was black smoke, and what appeared to be like red embers in the air."
Tina Smith, another nearby resident, said her house also shook. "We thought it was a sonic boom, because the Navy flies over a lot. But then we heard a really loud whooshing sound, and then we heard the sirens over at the refinery going off."
One woman died of burn injuries at Harborview Medical Center in Seattle, and three other employees, a woman and two men, remained in critical condition with burns over most of their bodies.
The fire was controlled within about an hour and a half, and parts of the refinery remained open Friday.
A nationwide inspection of petroleum refineries was launched in 2007 as a result of an explosion and fire in 2005 at a BP refinery in Texas that killed 15 employees and injured 170 others.
As part of that inquiry, the state Department of Labor and Industries announced it had cited Tesoro for 17 serious health and safety violations among 150 overall deficiencies.
Department spokeswoman Elaine Fischer said it initially proposed a fine of $85,700, but that was reduced to $12,250 as a result of a negotiated settlement. The agreement required Tesoro to abate all hazards and hire a consultant to oversee safety management. A report on compliance is due in May, Fischer said.
The department has also sent investigators to the scene.
Horowitz said the Chemical Safety Board would try to determine the reasons for the proportionately large number of refinery accidents in recent years.
"There are about 150 oil refineries that are active, and there are tens of thousands of chemical and other hazardous materials plants. We're seeing a disproportionate number of accidents at refineries, and they're quite serious in many cases," Horowitz said.
He said a number of recent accidents have stemmed from "mechanical integrity" problems, such as failure of piping, equipment or valves.