- Associated Press - Tuesday, April 1, 2014

A large explosion rocked a natural gas processing plant on the Washington-Oregon border Monday, injuring five workers, causing about 400 people to evacuate from nearby farms and homes, and emitting a mushroom cloud of black smoke that was visible for more than a mile.

The 8:20 a.m. blast at the WilliamsNorthwest Pipeline facility near the Washington town of Plymouth, along the Columbia River, sparked a fire and punctured one of the facility’s two giant storage tanks for liquefied natural gas.

Benton County Sheriff Steven Keane said a relatively small amount of gas leaked from the tank to the ground in a moat-like containment area. But it then evaporated, blowing away to the northeast, he said.

“I think if one of those huge tanks had exploded, it might have been a different story,” Keane said.

The fire at the facility about 4 miles west of Plymouth was extinguished within a couple of hours.

One of the injured workers was transported to a Portland, Ore., hospital specializing in burns, he said.

Benton Fire District 1 Capt. Jeff Ripley said another four people were taken to local medical facilities. None of the injuries was believed to be life-threatening.

More than a mile away across the Columbia River, the explosion shook Cindi Stefani’s home.

“It was just a very loud boom,” she said. “I looked across the river and saw a giant mushroom cloud and flames at least a couple hundred feet high.”

Animals on neighboring farms were running around, she added.

“At that point we were pretty scared. I was thinking, ‘We need to get out of here.’”

Deputies went door to door to homes and farms within a 2-mile radius, evacuating about 400 residents as a precaution.

By Monday night, the evacuation zone had been reduced to a 1-mile radius, the Benton County Emergency Management agency said. Road and river restrictions were lifted.

About 75 people checked into a shelter set up in Oregon at the Umatilla County Fairgrounds, but emergency officials said few were expected to stay the night.

The evacuation was described as voluntary.

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