Tunnels collapsed

Al Jazeera's Anita McNaught, reporting from the mine, said the rescuers were having massive problems getting to the scene of the explosion because the tunnel walls had collapsed and because of the danger of explosive methane gas.

"The prognosis is not good," she said, referring to other recent explosions caused by methane gas.

"The blasts are usually extremely large, extremely high temperature.

"Not only do they collapse tunnel walls - they melt metal supports, they suck the oxygen out of the air, they replace it with carbon monoxide.

"It would be quite a miracle if any of these 30 remaining men were retrieved intact from what happened."

The trapped workers were extending and bolstering tunnels at the time of the explosion, a process that calls for the use of dynamite, the provincial governor said. But it was not clear whether the workers had in fact set off dynamite on Monday.

The force of the explosion knocked out electricity in the mine, damaged the communications system and blew out the windows of nearby buildings, media reports said.

Eight other workers, who were trapped in the elevator after the explosion, were rescued and at least two of them were brought to the local hospital for treatment for gas poisoning.

Deadly cave-ins

In February, 13 workers were killed when a methane explosion caused a mine in Turkey's northwestern Balikesir province to cave in.

Also in the northwest, 19 workers lost their lives in a cave-in set off by an explosion in a mine in December.

According to official statistics, more than 2,700 workers have been killed in mining accidents since 1955.

The worst such accident happened in 1992 when 263 workers were killed in a gas explosion in a mine in Zonguldak where the current rescue operation is under way.