April 1 (Reuters) - An evacuation zone around a damaged liquefied natural gas facility in Washington state was scaled down late Monday following an earlier explosion as there was a reduced risk of another blast from a leaking storage tank, an official said on Tuesday.
A pipeline explosion at 8:22 a.m. Pacific time (1522 GMT) Monday at Williams Cos Inc's LNG facility near the town of Plymouth in rural southeastern Washington state had hurt five workers and sent shrapnel into one of two storage tanks at the site, according to Benton County emergency responders.
Due to the risk of further explosions at the time, the Benton County Emergency Management office had evacuated residents within a two-mile (3.2 km) radius of the site and about 17 workers at the facility.
The county, later on Monday, shrank the evacuation zone to one mile, allowing most residents to return home, after emergency personnel determined there were no fires or leaking pipes, Brian Calvert of the Benton County Emergency Management office in Richland, Washington, told Reuters on Tuesday.
The evacuation zone was scaled down because the risk of harm from the leaking storage tank was reduced, Calvert said, adding he was not qualified to say if the tank could still explode.
"Liquefied natural gas poses a personal health risk including nausea and difficulty breathing and it is also a volatile explosive," he said.
Calvert said workers from Williams and emergency responders were expected to return to the site Tuesday to look for any leaking pipes and to begin securing the damaged storage tank.
The county also reopened a highway near the site to car traffic and the Columbia River, which is close to the site, to ship traffic, Calvert said.
Officials at Williams, an oil and gas company based in Tulsa, Oklahoma, were not immediately available for comment.
On Monday night, Williams' officials said the leaking gas had evaporated and there was no indication dangerous vapors were drifting into the town of Plymouth, which has about 400 residents.
Early Tuesday, Michele Swaner, a Williams spokeswoman who was traveling to the site, said on her voice mail that all but a few of the evacuated residents were allowed to return home Monday night and the company expected to have workers on site later Tuesday.
Five workers were injured by Monday's blast, with one suffering burns, while four others were hit by debris and taken to local hospitals, Joe Lusignan, a spokesman for the Benton County Sheriff's office said on Monday.
Each storage tank stands 133.5 feet tall and holds up to 1.2 billion cubic feet of natural gas. Together, the Williams' tanks can hold enough gas to meet nearly 3.4 percent of typical daily U.S. natural gas demand.
The company said each tank was around one-third full before Monday's explosion.
Williams said Monday it shut the connections from its main line, called the Northwest Pipeline, to the Plymouth facility.
The 3,900-mile-long (6,276-km-long) Northwest Pipeline, which delivers gas to and from several Western States, is still operating, the company said.
The incident had no discernible impact on U.S. natural gas prices, which mostly fell on Monday at Western gas hubs.
Shares of Williams gained 34 cents, or 0.8 percent, early Tuesday to $40.92 on the New York Stock Exchange, while shares of most other energy utilities were down. (Editing by Bernadette Baum)