BECKLEY, W. Va. - Witnesses described poor ventilation, methane buildup, and other safety violations to a congressional committee, but said fear of being fired kept miners working inside Massey Energy's Upper Big Branch mine before it was rocked by a deadly explosion.

Foremen inside the mine were also tipped off to the arrival of inspectors, a witness alleged, with efforts made to hastily correct violations or distract the inspector.

One of the dead miners, Dean Jones, was a section foreman, and a family member on Monday told the House panel that Jones had expressed fears about inadequate ventilation inside Upper Big Branch but felt compelled to continue working.

Alice Peters, Jones' mother-in-law, said he had said to her that "at least seven times, he was told by Massey supervisors that, if he shut down production because of the ventilation problems, he would lose his job."

Jones' son, Kyle, has cystic fibrosis and requires constant medical care, a situation that she said made her son-in-law especially fearful of being fired.

The Upper Big Branch mine, near Beckley, exploded on April 5, killing 29 workers.

House Education and Labor Committee Chairman George Miller (D., Calif.) was sharply critical of Massey.

Miller said his panel understood "the disastrous results when mine owners operate at the margins of safety in order to put more coal on the belt."

Massey's chief executive, Don Blankenship, has repeatedly said the company does not put profits ahead of safety.

The father of another fallen miner, Steve Morgan, said his son Adam told of floating explosive coal dust that was so thick that, at points, he could not see while working.

"He once told me that they were notified an inspector was on his way in and he was told to hurry up and apply rock dust to keep the float dust down," Morgan said.

In prepared remarks, Stanley Stewart said he worked at Upper Big Branch until the day of the explosion. Stewart told of poor ventilation and large amounts of methane seeping from the coal face.

"We knew that we'd be marked men and the management would look for ways to fire us" if people raised safety issues, Stewart said. "Maybe not that day, or that week, but somewhere down the line, we'd disappear."

The father of Gary Wayne Quarles, another of the 29 dead miners, alleged that managers at Upper Big Branch alerted one another when an inspector for the federal Mine Safety and Health Administration arrived.

"The code words go out that 'We've got a man on the property,' " Gary Quarles Sr. said. He said the tip would be radioed from the guard gates to operations underground.

Warning of an impending inspection is a civil violation of federal mining regulations, MSHA chief Joe Main said after the hearing.