Rescue teams have re-entered Russia's largest coal mine after a build up of gas halted the search for 83 people believed trapped underground.
More than 500 people were involved in efforts to reach the 64 miners and 19 rescue workers stuck in the Raspadskaya mine in Siberia's coal-rich Kemerovo region after it was it by two explosions late on Saturday.
"The rescue effort has restarted. Four teams have been sent into the mine," Valery Korchagin, a regional emergency official, said late on Sunday.
Russian news agencies said the teams were hoping to rescue five people trapped in one part of the mine.
Emergency workers were also trying to pump air into the mine to disperse the build-up of methane, which caused the two explosions that killed 12 people and injured 41.
Rescue operations involving over 500 people were suspended early on Sunday because of dangerous conditions and fears of further blasts.
'Serious situation'
Vladimir Putin, the prime minister, urged rescue officials in a televised video conference to "do everything technically possible so the mine is ventilated in the shortest possible time".
"The situation is clearly serious."
Around 300 people emerged from the mine after the first explosion, the prosecutor general's office said in a statement, adding that at least 13 of them who were hospitalised were in serious condition.
The statement said that local prosecutors had opened a criminal investigation into possible safety violations.
The Raspadskaya mine, which is 500 metres deep and has 370km of underground tunnels, produces about eight million tonnes of coal a year, according to the company's website.
Mine explosions and other industrial accidents are common in Russia and other former Soviet republics, and are often blamed on inadequate implementation of safety precautions by companies or by workers.
In December, nine people were killed in an explosion at an iron-ore mine in the Urals Mountains region that was blamed on faulty transportation of explosives.
In 2007, a blast at the Ulankovskaya coal mine, also in Kemerovo, left more than 100 people dead.
The authorities had announced in the aftermath of that blast that all surrounding mines would be checked for safety.