By Matt Pearce, Los Angeles Times

The owner of a natural gas facility downplayed the danger to residents after an explosion at the facility injured four people and forced the evacuation of a small town in southern Washington on Monday morning.

The processing facility is owned by Northwest Pipeline, a subsidiary of Williams Partners, a Tulsa, Okla.-based energy company. The facility is located 2 miles west of Plymouth, whose 300 to 400 residents were ordered to evacuate after the 8:20 a.m. blast.

The company was investigating the cause of the explosion. But Williams Partners said it did not appear to have been caused by a pipeline rupture but rather occurred inside a liquefied natural gas storage facility, according to a statement from the company.

The facility’s employees were evacuated, and at least one worker was injured, the company said. (The other three injured were reported by sheriff’s officials; it wasn’t immediately clear who they were or the extent of their injuries.)

Concerns about further danger arose after the blast sent debris and metal shrapnel into a 1.2-billion-cubic-foot storage tank that was at least partly filled, Benton County Sheriff Steve Keane told the Los Angeles Times.

The tank began to leak, sending out fumes, he said. The facility was “immediately shut down” and then evacuated after the explosion, the company said in a statement.

It downplayed the possibility of further danger to residents.

“We believe that only natural gas was released and it evaporated into the atmosphere,” Williams spokesman Tom Droege said in the statement. “There is no hazardous vapor drifting toward residents in the area. The tanks involved were about one-third full of liquefied natural gas.”

Sheriff Keane said authorities had evacuated residents to Umatilla, Ore., just across the Columbia River, as a precaution.

Photo: Tim Evanson via Flickr