Nine miners have been trapped by smoke inside a mine of Russian potash producer Uralkali, the company says.
Uralkali said a rescue operation was under way on December 22 after an incident at a mine in Solikamsk, northeast of the capital, Moscow.
The Russian company said the trapped miners were employees of a subcontractor doing maintenance work.
The subcontractor's chief, Andrei Maksimov, told the Interfax news agency that the chances of finding the trapped miners alive were slim.
Earlier, an unnamed source in the emergencies services told the Russian news agency TASS that rescuers had so far not been able to reach the miners.
"Mine rescuers cannot reach nine people so far due to high temperature and smoke. There are about 10 meters left," he said, adding that rescuers had no connection with the miners.
The source said 17 people had been in the mine when the fire broke out.
According to the source, eight of them have been evacuated and are safe.