Rescuers struggled to reach more than 200 miners trapped underground early Wednesday after an explosion and fire at a coal mine in western Turkey killed at least 201 workers, authorities said, in one of the worst mining disasters in Turkish history.

Energy Minister Taner Yildiz said 787 people were inside the coal mine in Soma, some 250 kilometers (155 miles) south of Istanbul, at the time of the accident and 363 of them had been rescued so far.

At least 80 miners were injured, including four who were in serious condition, Yildiz told reporters in Soma, as he oversaw the rescue operation involving more than 400 rescuers.

The accident occurred when the workers were preparing for a shift change, officials said, which likely raised the casualty toll because there were more miners inside the mine than usual.

Yildiz said the deaths were caused by carbon monoxide poisoning and feared the death toll could end up much higher than the latest count of 201 workers.

The rescue effort is “reaching a critical stage,” Yildiz said, with more deaths likely as time passes.

Earlier, the minister said the rescue operations were hindered because the mine had not completely been cleared of gas.

Authorities say the disaster followed an explosion and fire caused by a power distribution unit.

“Time is working against us. We fear that the numbers could rise further,” Yildiz said. “We have to finish this (rescue operation) by dawn. I have to say that our pain, our trouble could increase.”

Earlier Yildiz said some of the workers were 420 meters (460 yards) deep inside the mine. News reports said the workers could not use lifts to get out of the mine because the explosion had caused a power cut.

Earlier, television footage showed people cheering and applauding as some trapped workers emerged out of the mine, helped by rescuers, their faces and hard-hats covered in soot. One wiped away tears on his jacket, another smiled, waved and flashed a “thumbs up” sign at onlookers.

There was no information on the condition of those trapped. But the disaster management agency said authorities were preparing for the possibility that the death toll could jump dramatically, making arrangements to set up a cold storage facility to hold the corpses of miners recovered from the site

Turkish Prime Minister Recep Tayyip Erdogan, who had cancelled a trip to Albania, was headed for the disaster site, Turkish media reported.

The former head of the miners’s union in Turkey, Çetin Uygur, said the incident was “truly a workplace murder of the highest degree,” as quoted in the newspaper.

Mining accidents are common in Turkey, which is plagued by poor safety conditions.

Turkey’s worst mining disaster was a 1992 gas explosion that killed 263 workers near the Black Sea port of Zonguldak.