The families of six men killed in a Utah mine cave-in last year sued the mine's owners Wednesday, claiming that the collapse occurred because they were harvesting coal unsafely.

The lawsuit filed in 3rd District Court contends Murray Energy Corp. and its affiliates knowingly continued to perform risky retreat mining last summer, despite a mountain "bounce" in March 2007.

"It was a preventable tragedy," Colin King, one of several attorneys representing the families, said at a news conference Wednesday. "They were gambling with the safety of the miners.

A thunderous collapse, so powerful it registered as a 3.9 earthquake, trapped the men in the Crandall Canyon mine on Aug. 6. Their bodies remain entombed there. Three other men were killed 10 days later trying to tunnel in to rescue the miners.

Court papers contend that the March 2007 bounce — a violent ejection of rock and coal from the mine's ribs, roof or floor — was ample evidence of the danger. It accuses Ohio-based Murray Energy and others of being "motivated by avarice and greed at the expense of safety and human life" in continuing to extract coal.

An attorney for Murray Energy called the allegations of negligence "blatantly false and unnecessarily hurtful."

Kevin Anderson said comments by the families' legal team were intended to "smear" Murray Energy chief Bob Murray "with half-truths and innuendo."

Anderson denied any wrongdoing by Murray Energy and said much of the lawsuit points to events that preceded its ownership.

"What happened at the Crandall Canyon mine last August was a horribly tragic and completely unforeseen event of immense and unprecedented magnitude," he said. "Our clients did not cause this."

Murray has insisted that the collapse was caused by an earthquake.

Murray Energy purchased Crandall Canyon in August 2006 and shares ownership with the Los Angeles Department of Water and Power and the Intermountain Power Agency, a utility consortium comprised of about two dozen Utah municipalities.

IPA and LADWP are also defendants in the lawsuit. In a joint statement, they did not comment on the allegations but said they respected the families' right to go to court.