Opponents blamed Prime Minister Tayyip Erdogan's government for ignoring repeated warnings about the safety of the country's mines.
"We as a nation of 77 million are experiencing a very great pain," Erdogan told a news conference after visiting the site, at which he gave the figures for those confirmed dead and still thought missing. But he appeared to turn defensive when asked whether sufficient precautions had been in place at the mine.
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"Explosions like this in these mines happen all the time. It's not like these don't happen elsewhere in the world," he said, reeling off a list of global mining accidents since 1862.
Fire knocked out power and shut down ventilation shafts and elevators shortly after 3 pm (1200 GMT) on Tuesday. After an all-night rescue effort, emergency workers pumped oxygen into the mine to try to keep those trapped alive. Thousands of family members and co-workers gathered outside the town's hospital searching for information on their loved ones.
"We haven't heard anything from any of them, not among the injured, not among the list of dead," said one elderly woman, Sengul, whose two nephews worked in the mine along with the sons of two of her neighbours.
"It's what people do here, risking their lives for two cents ... They say one gallery in the mine has not been reached, but it's almost been a day," she said.
The fire broke out during a shift change, leading to uncertainty over the exact number of miners trapped. Energy Minister Taner Yildiz said late on Tuesday 787 workers were in the mine at the time.
Initial reports suggested an electrical fault caused the blaze but Mehmet Torun, a board member and former head of the Chamber of Mining Engineers who was at the scene, said a disused coal seam had heated up, expelling carbon monoxide through the mine's tunnels and galleries.
"They are ventilating the shafts but carbon monoxide kills in 3 or 5 minutes," he told Reuters by telephone.
"Unless we have a major miracle, we shouldn't expect anyone to emerge alive at this point," he said, pointing to an outside chance that workers may have found air pockets to survive.
The disaster highlighted Turkey's poor record on worker safety and drew renewed opposition calls for an inquiry into a drop in safety standards at previously state-run mines. The International Labour Organization ranked the EU candidate nation third worst in the world for worker deaths in 2012.
Erdogan earlier declared three days of national mourning and cancelled an official visit to Albania. President Abdullah Gul also cancelled a trip to China scheduled for Thursday in order to travel to Soma.
"We are heading towards this accident likely being the deadliest ever in Turkey," Yildiz told reporters, adding that "hopes were dimming" of finding many more survivors.
A pall of smoke hung above the area and Yildiz said the fire was still burning underground, hampering the rescue operation.
Some 93 people were rescued, including several rescuers who had themselves become trapped or overcome by fumes, and 85 were being treated for their injuries, Turkey's disaster management agency AFAD said in an email.