The operator of the Turkish mine that collapsed, killing at least 284 people, has denied any negligence.
Representatives from Soma Holding defended their response to the disaster, telling a news conference their priority had been to save lives.
They added that an unexplained build-up of heat in the mine appeared to have caused the collapse.
Meanwhile, riot police are using water cannon to disperse several thousand protesters in Soma.
They are trying to break up what had appeared to be a peaceful demonstration, with protesters chanting in support of the miners, reports the BBC's James Reynolds from the scene.
There have been angry anti-government protests across the country for the last three days over what has become Turkey's worst-ever mine disaster.
Up to 18 workers are believed to be still trapped inside the mine, according to Turkish ministers and Soma Holding. It is not clear if the men are still alive.
Another 363 escaped, while 122 are injured.
The disaster began when an explosion on Tuesday sent carbon monoxide gas into the mine's tunnels while 787 miners were underground.
Energy Minister Taner Yildiz said that a fire was still burning inside the mine, but it was "declining".
Anyone negligent about safety at the mine would be punished, he said, adding: "We won't take any notice of their tears".
'We want answers'
Speaking to journalists, plant manager Akin Celik said: "We still do not know how the accident happened. There is no negligence of ours in this incident."
"We want to find answers as well. We have never faced such conditions, such circumstances. We haven't slept for three days because we're first trying to save lives."
Soma Holding executives said it was not clear what caused the explosion and collapse.
However, General Director Ramazan Dogru said reports that the fire began at a transformer were wrong.
"Overheating led to a collapse" at another part of the mine, he said, adding that this caused a fire which rapidly expanded. He said it was not clear why the overheating had occurred.
Much of the news conference focused on whether the mine had rescue chambers - safe rooms where miners can take refuge for an extended period of time.
Mining officials said an existing rescue chamber at the mine's upper levels had been disassembled as production there had stopped, and work on a rescue chamber at the lower section was under way.
Rescue chambers were not a legal requirement, and the mine had an escape route for workers, they added.
Company chief Alp Gurkan said he was "saddened" by the disaster, and that he "couldn't believe what [he] was hearing" when he heard the news.
"All the high-level mining experts in Turkey have seen this as the safest mine. We have difficulty in understanding how this event has happened," he said.
Prime Minister Recep Tayyip Erdogan has been criticised for being insensitive in his reaction to the disaster, by appearing to suggest that it was a fact of life.
His aide Yusuf Yerkel made headlines on Thursday when photos emerged of him appearing to kick a protester in Soma.
Later pictures of Mr Erdogan appearing to slap a protester in a local supermarket were also shown in the Turkish media.
In an interview with the BBC, the deputy chairman of Turkey's governing Justice and Development Party Huseyin Celik said Mr Yerkel "was apparently overwhelmed by his emotions" and had been attacked by a protester.
The government did not approve of Mr Yerkel's actions, he said.
He said the accusation against Mr Erdogan was an example of people "making such claims to increase tension in the country".
The Soma mine was privatised in 2005. The government has been accused of rejecting a recent proposal for an inquiry into mine accidents, but officials say the Soma mine was subject to regular inspections, most recently in March.