The accident - the worst in Ukraine in seven years - highlighted the lack of attention to safety in a country with some of the world's most dangerous mines.
Local authorities declared three days of mourning for the dead miners.
A total of 457 people were working in the mine at the time.
Mykola Maleyev, an official with Ukraine's work safety authority, said at least 350 miners had since been evacuated.
"[But] work has been complicated by the fact that the incident has affected the ventilation system," Maleyev said.
Trade unionists said smoke was hampering rescue efforts.
|Police at the entrance to the Zasyadko mine [AFP]|
"There is thick smoke in the shafts and, for the moment, rescue teams are unable to go where they are needed," one trade union official at the mine, who spoke on condition of anonymity, said.
Several fatal accidents have occurred at the Zasyadko mine in the past. The mine is one of Ukraine's largest, employing about 10,000 people and producing up to 10,000 tonnes of coal every day.
A gas leak in September 2006 killed 13 miners.
In 1999, an explosion claimed 50 lives, while in 2001 another explosion killed 50 people, and 20 people were killed in an accident in 2002.
Official statistics put the total death toll in mining accidents in Ukraine this year at 80, though independent trade unions say the figure is higher. Last year, 170 miners died.
Post-Soviet Ukraine's most deadly mining accident was in March 2000, when 80 miners were killed in a coal dust explosion at a colliery near the eastern town of Luhansk.