The recovery operation is hampered by high temperatures in the mine
At least 12 people are now known to have been killed in a blast at a mine in north-west Russia, officials say.
Five people were injured in the overnight explosion at the mine near Kirovsk, in the Murmansk region.
Workers were conducting controlled explosions at the mine when the blast occurred, the officials said.
The mine is operated by OAO Apatit, a major Russian company that produces apatite - a mineral commonly used in making fertiliser.
"At the moment we know that 12 people died. Five were injured and they are in hospital," Russia's Emergencies Ministry spokeswoman Irina Gretskaya said.
"There were 18 people in the mine when the accident happened, so we do not know about one miner," she said.
Officials initially said nine people were killed.
Russia's mining safety watchdog has launched an investigation into the accident.
Many of Russia's mines have poor safety standards and have not been updated since the fall of communism.