MIKE STARK Associated Press — November 16, 2009

SALT LAKE CITY (AP) — The Utah oil refinery where there was a huge gas explosion earlier this month is shutting down until investigators can determine it's safe to reopen, federal officials said Friday.

The Nov. 4 blast at the Silver Eagle Refinery in Woods Cross damaged 10 nearby homes but caused no injuries.

The U.S. Chemical Safety Board has been investigating the explosion.

Officials in recent days had developed serious concerns about the plant's equipment, board Chairman John Bresland said in a statement. Bresland said he recommended to refinery officials Friday afternoon that the plant be shut down "as quickly and as safely as possible."

"It's the first time that we've ever suggested to a site that they stand down in this way," Daniel Horowitz, a spokesman for the U.S. Chemical Safety Board, said Friday afternoon.

Silver Eagle officials said that before Friday's meeting they were already taking steps to suspend some of the operations at the refinery, which employs about 60 people.

"We have decided to do this because our top priority is the health and safety of our employees and the community," Silver Eagle Refining President Dave McSwain said in a statement. "We believe this is the best decision given the circumstances."

The plant could be restarted once any needed repairs are made. Officials said it's unclear how long the refinery might be shut down.

Investigators haven't made a final determination on what caused the blast. Preliminary findings indicate that the explosion happened when a 10-inch pipe failed catastrophically. The pipe's "significant thinning" had not been detected by the refinery's inspection program, Bresland said.

He also raised concerns about a lack of documentation about the refinery's equipment.

Board investigators discussed their findings with state and federal workplace safety officials and Silver Eagle's president and chairman.

After the Nov. 4 explosion, a city building inspector condemned one nearby house as structurally unsound after the blast shifted it off its foundation and loosened a roof truss. Officials feared the house could collapse in high winds.

The explosion came as investigators were still trying to determine the cause of a fire earlier this year.

On Jan. 12, four people were seriously burned at Silver Eagle when a 440,000 gallon storage tank caught fire and burned for 11 hours. Federal investigators said the ignition source may have been a gas heater or a refrigerator's electric outlet in a utility shed about 160 feet from the tank.

The refinery also had fires in 2003, 2005 and 2007, according to federal records.

The Woods Cross refinery ranks 130th in production among U.S. refineries at an operable capacity of 10,250 barrels a day, according to the Energy Information Administration.