A cave-in killed three rescue workers at a Utah mine while they looked for six trapped miners, and the U.S. state's governor demanded on Friday that the underground search stop until safety could be ensured.

Whatever it is, we as a state don't want any more injuries. We've had enough, Utah Gov. Jon Huntsman told an early Friday news conference.

The cave-in, which occurred about 6:35 p.m. MDT (8:35 p.m. EDT), was called a mountain bump -- an eruption of rock and coal under increased pressure from overhead rock as drilling removes surrounding rock and material shifts.

The deaths of the three workers along with the injury of six others compounded the disaster which began 11 days ago when part of the Crandall Canyon Mine near Huntington, Utah, collapsed, trapping the six miners still missing.

Huntsman said he was pushing to cease below-ground efforts to find the trapped miners unless federal mine safety officials could guarantee the safety of the workers.

Above-ground drilling efforts to locate the miners will be the best source of information, Huntsman said, and work at the central Utah site should proceed with a focus like never before on workplace and worker safety.

Crandall Canyon Mine co-owner Robert Murray said on Thursday the cavity found by a third bore hole had enough oxygen to sustain life indefinitely and that his crews would keep up efforts to contact the missing men.

CAUSE UNCLEAR

It remains unclear what caused the mine to collapse earlier this month. Murray has said it was triggered by an earthquake despite disagreement from geologists.

Central Utah has long been rich not just in coal deposits, but also the great fortunes and deep despair that come with pulling it from the ground.

Monuments and museums to past accidents and tragedies mark the roads and towns in the center of the state.

The list of accidents stretches back at least to May 1900, when 200 men were killed by an explosion in the Winter Quarters Mine, one of the worst mining accidents in U.S. history.

In 1924, 172 men died in a series of explosions or of carbon monoxide poisoning at a mine in Castle Gate. In 1984, a fire in the Wilberg Mine killed 26 men and one woman.

The mines have been a source of work for immigrants for more than a century. Today, many miners are from Mexico and other Latin American countries.

Spanish-language television crews are among the media that have descended on the area, and according to mine officials, the six miners trapped in the Crandall Canyon mine include three Hispanics.

Controversy had also risen over reports that the miners were engaged in dangerous retreat mining when the shaft collapsed. Murray has denied such a technique was being used.

Retreat mining involves supporting a mine's roof with a column of coal, then removing those pillars and allowing the shaft to collapse as miners move to safety.

The Crandall Canyon Mine is on a high desert plateau some 140 miles south of Salt Lake City, in what is known as Utah's castle country because of the towering rock spires that dot the rugged landscape.