coal mine blast in northern China

At least 87 people are now known to have died in a coal mine blast in northern China, state media report.

Another 21 miners are reportedly still missing in the Xinxing pit in Hegang City, 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.

The death toll makes the accident among the worst in recent years in China's notoriously dangerous mines.

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.

Xinhua said President Hu Jintao and Prime Minister Wen Jiabao had been in contact with rescue workers, and that Vice Premier Zhang Dejiang had visited the scene.

Lax safety

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.

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

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.

The BBC's Michael Bristow in Beijing says it appears that a build up of gas was the cause of the explosion.

The mine is operated by the state-owned Heilongjiang Longmei Mining Holding Group and has an annual capacity of 1.45m tonnes of coal, said Xinhua.

The authorities are likely to be concerned that the accident happened in a state-run mine, says our correspondent.

They are generally considered to be safer than private collieries, whose lax safety standards have contributed to a high rate of accidents.

Most incidents are blamed on a failure to follow safety guidelines, often in an attempt to cut costs and meet an increasing demand for fuel.

The Chinese authorities have been trying to deal with the dangers by closing smaller mining operations and forcing local authorities to regulate the industry.

The government closed some 1,000 small mines in a recent safety drive, and says the number of miners killed has been halved as a result.

But miners are still dying at a rate of six a day, and independent labour groups say many accidents are covered up in the drive for profit and coal.

In February, more than 70 workers were killed in an explosion at a mine in Shanxi province.