Earthquake rumble

Murray insists an earthquake that lasted several minutes caused the mine collapse, and several aftershocks have plagued rescue efforts. However, scientists again said they believe it was the mine collapse that registered a 3.9 on the Richter scale.

"All the data suggests it's a mine collapse," said Rafael Abreu, a geologist with the U.S. Geological Survey's National Earthquake Information Center in Golden, Colo.

Speaking to reporters today, Murray again dismissed the scientists' assertion and said he would no longer speak about it.

"From our mining experience, we know this was an earthquake," he said.

The University of Utah Seismograph Stations said it has not ruled out conclusively that an earthquake was not involved but said all of the seismic events appear to be consistent with a mine collapse.

MSHA officials said there will be an "exhaustive" investigation to determine what caused the collapse. On the scene, assistant U.S. Labor Secretary Richard Stickler would not speculate on the cause, or whether so-called "retreat" mining had anything to do with it.

"I assure you, by the end of that investigation, we will have the answer," he said.

Murray Energy has said it was not conducting that type of mining, in which pillars holding up the roof of a mine shaft are pulled and it caves in. The leftover coal is then harvested.

MSHA officials in Washington, D.C., confirmed to the Deseret Morning News that the Crandall Canyon Mine had been conducting retreat mining. A plan filed by the mine was approved by federal authorities, said MSHA spokeswoman Amy Louviere.

"What we have emphasized is that as long as the roof control plan is followed, it can be a very safe method for mining," she said.

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Contributing: Amy Joi O'Donoghue

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E-mail: twalch@desnews.com; bwinslow@desnews.com