Fear of a second gas explosion was slowing efforts to find 15 coal miners missing 3,300 feet underground after a blast that killed at least eight of their colleagues.

The accident happened Tuesday afternoon as the men, aged between 21 and 59, were retrieving equipment from a dangerous section of the Halemba mine in the southern city of Ruda Slaska.

Grzegorz Pawlaszek, head of the state-owned Coal Co., said rescue teams had recovered seven bodies from the scene of the blast. Another body had been located but could not be reached because the high concentration of methane gas meant there was the risk of another explosion.

He said the fate of the other 15 was "not known."

Locator devices carried by the missing miners were emitting no signals. Still, "there is a chance to find someone still alive," Palwaszek said.

He said rescuers were monitoring the concentration of gas seeping out of the rock before deciding whether to move further ahead through the rubble-filled tunnels.

He said the affected shaft was closed in March because high gas concentrations made further work there too dangerous. However, equipment worth$23 million was left behind.

"It was new equipment and that is why we decided to retrieve it," Pawlaszek said, adding the work was done under increased security and under the supervision of specialists in detecting gas.

He said the recovered bodies had burns and were hard to identify because ID tags were torn away in the blast.

Earlier, company spokesman Zbigniew Madej said 15 rescue workers were digging their way through 500 yards of rubble in the hope of finding survivors but said ventilation systems had been damaged.

"The situation is very, very serious," Madej said.

Inside the mine complex, officials and priests were counseling distraught relatives seeking word on missing loved-ones. Eight white candles were burning on a low wall outside the main gate.

Miners leaving the premises early Tuesday after completing their shifts in parts of the mine still operating were downcast.

"There is fear," said Krzysztof Przybyla, a 34-year-old who said he knew some of those trapped. "This could have happened to any of us."

Labor unions complain that a lack of investment and massive layoffs in recent years have resulted in falling safety standards at the nation's mines.

The Halemba mine, located in the heart of the Silesia industrial region, opened in 1957, making it one of the oldest, and has a record of serious accidents.

In 1990, 19 miners were killed and twenty injured in a gas explosion there and a 1991 cave-in killed five more. Earlier this year, a Halemba miner was rescued after he spent five days underground following a gas explosion.

Poland's worst mining accidents were in 1974 and 1979 when explosions killed 34 miners each at the Czechowice-Dziedzice in Silesia and the Dymitrow mine in Bytom.

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