At least 87 people are now known to have died in China's worst coal mine accident in two years, state media say. Another 21 miners are missing after the blast at Xinxing pit in Hegang City in Heilongjiang province.
The toll has more than doubled from 42 dead earlier. Some 528 workers were in the mine when the blast hit before dawn on Saturday local time, said Xinhua.
A top official, Vice Premier Zhang Dejiang, has been sent to oversee rescue efforts at the state-owned mine.
President Hu Jintao and Prime Minister Wen Jiabao had also been in contact with rescue workers, state media said.
China's central government has made improving safety standards a priority, but rules are often ignored in favour of profit.