PRICE -- The operator of a collapsed Utah mine violated safety protocols by cutting coal pillars that should have been left standing to prevent cave-ins, federal regulators said Thursday.

The officials said a subsidiary of Ohio-based Murray Energy Corp. undermined other pillars by excavating coal from tunnel floors. They also faulted the company's engineering firm, Agapito Associates Inc. of Grand Junction, Colo., for conducting a flawed evaluation of mining dangers.

Murray Energy chief Bob Murray has insisted that retreat mining, as taking down pillars is called, had nothing to do with the collapse. He argued from the start that it was caused by an earthquake.

At a news conference Thursday, Mine Safety and Health Administration chief Richard Stickler disputed that, instead blaming poor engineering.

"First of all, it was not -- and I'll repeat not -- a natural occurring earthquake, but in fact it was a catastrophic outburst of the coal pillars that were used to support the ground above the coal seam," Stickler said.

The agency is fining Murray Energy affiliate Genwal Resources Inc. $1.6 million and Agapito $220,000 for the disaster.

Stickler said the proposed fines, which Murray can appeal, are the largest imposed on a coal mining operation in MSHA's history.

The Aug. 6 collapse trapped six miners whose bodies have never been recovered. Three others were killed during a rescue attempt.

MSHA said Genwal misled regulators about the dangers and violated its approved mining plan.

Genwal Resources responded in a lengthy statement contending "politics" and congressional meddling corrupted the MSHA investigation.

"This report does not have the benefit of all of the facts and appears to have been tainted by ten months of relentless political clamoring to lay blame for these tragic events," the company said.

Agapito Associates said it hadn't had a chance to study the report and couldn't offer any immediate comment.

Wendy Black, a widow of one of the rescuers, said she had trouble understanding why officials uncertain of the mine's stability were willing to send in a rescue team.

"How could they let the rescuers go in?" she asked.

Her husband, Dale "Bird" Black, was at the head of the rescue team, operating a 65-ton grinding machine that bored its way through the rubble toward the trapped miners on Aug. 16. Black took the full brunt of the second cave-in and died instantly, a medical examiner told his widow.

Colin King, a lawyer for families suing Murray Energy and affiliates, said the report showed that the company failed to properly report early signs of trouble. MSHA officials said they weren't made aware of a partial collapse of another section of the mine in March 2007, seven months before the fatal summer cave-ins.

And in a previously unreported incident, the report said Genwal Resources failed to report a coal "outburst" on Aug. 3 that half-buried an equipment operator in loose coal. The operator was uninjured, according to the report.

A second report issued Thursday by the U.S. Department of Labor faulted MSHA for failing to properly evaluate the engineering and roof-control plans at Crandall Canyon.

The department's 201-page report also said MSHA failed to take into account early signs of danger when it approved retreat mining, and failed to conduct a formal risk analysis for the rescue effort.

MSHA tapped a district manager, Richard A. Gates of Birmingham, Ala., as chief of the investigative team. Six other members are career MSHA officials.

Their 472-page report confirmed congressional investigations that faulted Genwal for courting danger at the mine.

Internal company memos revealed that the company was digging into massive blocks of coal that should have been left standing to hold the mine up, according to a March report issued by Sen. Edward Kennedy's Health, Education, Labor and Pensions Committee.

The same report found that the company was excavating coal from tunnel floors, undermining other coal pillars straining under the tremendous weight of the mountain.

MSHA's report said the operator didn't have permission to mine the "bottom coal." Yet internal company memos made no secret of the practice, which continued to within days of the collapse.

The cave-in left the six miners entombed in the mountain -- Kerry Allred, 58; Don Erickson, 50; Luis Hernandez, 23; Carlos Payan, 22; Brandon Phillips, 24; and Manuel Sanchez, 42. Other members of the rescue team killed Aug. 16 were Brandon Kimber, a 29-year-old miner, and Gary Jensen, 53, an accident investigator for the mining agency.

Kristin Kimber, the ex-wife of rescuer Brandon Kimber, said the report provides her with some sense of closure.

"Now we know the complete truth and we can move on from here," said Kimber, a mother of three. "But there are people I feel who need to be held accountable for their decisions and their actions ... that's what I'm looking forward to."