CHEYENNE, Wyo. (AP) -- An explosion has killed three workers who had been laying a fuel line at a Wyoming oil storage site, an oil company spokesman said.

The blast at about 10 a.m. Monday near Glenrock, in a remote region of eastern Wyoming, sparked a 10-acre fire before it was brought under control, Samson Resources Co. spokesman Dennis Neill said. The fuel line where the blast victims had been working was intended to supply a heater treatment facility that separates oil from water as they're pumped out of the ground.

The workers were employed by a contractor that the Tulsa, Okla.-based Samson had been hired to bring an oil well back into production at the site, Neill said. The well wasn't involved in the explosion and fire, which happened on the Hornbuckle Ranch, about 50 miles northeast of Casper.

Neill declined to name the company that employed the workers. Samson officials were traveling to the area, and state and federal investigators were on the scene, he said.

Neill said local and federal authorities are investigating the explosion, with the cause still unknown Tuesday. Authorities have not named the three workers.

"Obviously we're very concerned about the family and friends in this situation," Neill said.

Tina Wells, spokeswoman for Samson, said Tuesday that the company intended to release a statement on Tuesday. She said no information was available in advance of that.

Wyoming administers its own workplace safety program through the Department of Workforce Services.

J.D. Danni, manager of the Wyoming Occupational Safety & Health Administration program, said Tuesday that his office has two investigators on the scene of the explosion.

Danni said they will prepare a report on the cause of the explosion within 180 days. The report will look at the cause of the explosion as well as whether any workplace safety violations contributed to it, he said.

Danni said he didn't know whether there were any other witnesses to the explosion. He said his office is still confirming the names of the victims and the company they worked for. He said Samson hasn't received any citations from the state in recent years.

In July, a newly built gas pipeline exploded in northeastern Wyoming. No one was hurt, but the blast could be heard 10 miles away and left a 50-foot-long trench in the ground.

In 2006, a gas well blowout near Yellowstone National Park spewed a cloud of explosive natural gas, forced evacuations for miles around and polluted the drinking water. The cause is still unknown.

The Wyoming Department of Workforce Services reported last week that the number of occupational fatalities in the state rose to 34 last year - an increase of nearly 79 percent from the year before. Of those 34 workplace deaths, 10 were in natural resources and mining.

A bill that would have increased employer penalties for workplace safety violations was rejected early last year in the Wyoming State Senate. Then-Gov. Dave Freudenthal had urged passage of the bill, which had been supported by industry groups.

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