At least 92 people are now known to have died in China's worst coal mine accident in two years, state media say.
Another 16 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 mines are notoriously dangerous. The central government has made improving safety standards a priority, but rules are often ignored in favour of profit.
The blast in the mine, in the region bordering Russia, occurred at 0230 local time on Saturday (1830 GMT on Friday). More than 400 people managed to escape.
Many of the injured were being treated at the Hegang Mining Bureau Hospital, which said all 800 of its medical workers had joined the rescue operation, Xinhua reported.
Rescue official Zhang Fucheng was quoted by Reuters news agency as saying that attempts to reach the trapped miners were being hampered by dense gas and collapsed tunnels. No-one has been rescued alive since Sunday morning.
But a spokesman for the mining company, San Jingguang, said he believed the remaining 16 men were still alive and that rescuing them was the "first priority".
The BBC's Michael Bristow in Beijing says it appears that a build-up of gas was the cause of the explosion.
One of the rescued miners, Wang Xingang, said the blast knocked him out briefly.
CHINA'S WORST MINE DISASTERS
Feb 1950: Yiluo mine, Henan province - 174 dead
May 1960: Laobaidong mine, Shanxi province - 684 dead
Sept 2000: Muchonggou mine, Guizhou province - 162 dead
Nov 2004: Chenjiashan mine, Shaanxi province - 166 dead
Feb 2005: Sunjiawan mine, Liaoning province - 210 dead
Nov 2005: Dongfeng mine, Heilongjiang - 171 dead
Aug 2007: Xintai City, Shandong province - 181 dead
Dec 2007: Rui Zhiyuan mine, Shanxi province - 105 dead
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