Unannounced inspections at the only two mines doing retreat mining in Pennsylvania found that are operating safely, the state Department of Environmental Protection said.

The findings were announced late Tuesday, after DEP inspectors visited Dana Mining Co.'s Titus Mine in Dunkard, Greene County, and UAE Co.'s Harmony Mine in Coyngham, Columbia County, two relatively small deep mines that employ retreat mining similar to that reportedly done at the mine in Utah where six miners have been trapped by a cave-in for more than a week.

In retreat mining, coal pillars supporting the roof of an underground mine are removed sequentially and the mine roof is allowed to collapse as mining operations move, or "retreat," back toward the mine's entrance.

The practice has been used for more than 50 years, but coal mining safety experts say it can add risks, especially in mines that are particularly deep, like the Crandall Canyon mine in Utah, which operated more than 2,100 feet below the surface.

Gov. Ed Rendell ordered the inspections to ensure that the mining technique is being done safely in the state, said DEP Secretary Kathleen McGinty, who noted that all Pennsylvania bituminous mines are inspected quarterly and all anthracite mines are checked every two months.

The Titus Mine employs 30 and mines 172,000 tons of bituminous coal a year. The Harmony Mine digs 170,000 tons of anthracite annually and employs 43.

State mine inspectors checked the two mines to determine if they are operating in compliance with their permitted roof control plans, which ensure that mine roofs are stable until the coal pillars are extracted and miners vacate the area before the roof is allowed to collapse.

Neil Weaver, a DEP spokesman, said inspectors spent all of Monday at the Titus and Harmony mines reviewing maps and mining plans, including roof control plans, and inspecting machinery and equipment used underground.

Pennsylvania has not had a fatality related to retreat mining since September 1990, when a roof bolter at Dynamic Recovery Co.'s mine in Pitt Gas, Greene County, was crushed in a tunnel roof collapse.

What happened in the Utah mine collapse is unclear and will be investigated by the federal Mine Safety and Health Administration, which accepted a roof control plan amendment from the company in June that allowed retreat mining to occur in the southern tunnels of the Crandall Canyon Mine, where the six trapped miners were working.

That mining plan amendment was accepted despite concerns about poor roof conditions and a roof collapse that halted mining in a northern section of the mine in March, according to a report by The Salt Lake Tribune.

The northern tunnels are about 900 feet from the tunnels where the trapped miners were working.

Robert Murray, president and chief executive officer of Murray Energy Corp. of Cleveland, and co-owner of the Crandall Canyon Mine, has said he was not aware of any problems in the mine in March.

Mr. Murray, who purchased his half share of the mine last August, also has denied that retreat mining was used in the Crandall mine or caused the mine collapse that trapped the miners. He has maintained that an earthquake caused the collapse, even though seismologists say that is unlikely.