Chinese rescue teams say it might be more than two weeks until they can save a group of miners trapped hundreds of metres underground.

They have been trapped since an explosion closed the entrance tunnel to the Hushan gold mine in Shandong province on 10 January.

Authorities made contact with 11 surviving miners a week after the blast, but one has since died.

Rescuers have drilled small holes to supply food and medicine to the men.

The cause of the explosion that sealed the mine entrance is still not known.

The fate of another 11 miners trapped by the blast is unclear - authorities have been unable to communicate with them despite lowering food and messages into other areas of the mine.

The group discovered alive told rescuers they had established communication with a lone miner about 100m below them, but had since lost touch with him.

Currently, rescue operations are trying to widen a narrow shaft to make it big enough to lift the miners out.

However, drilling is proving difficult as it needs to get through particularly hard granite and the miners are trapped far from the surface. Rescuers face an added problem in that the mine is waterlogged and there's the risk the chamber where the miners are stuck could flood.

"The obstacles are just too huge, which means we need a least another 15 days or even more to reach the miners," Gong Haitao, deputy head of the local publicity department, said.

The debris standing in the way weighs about 70 tons, he added.

The entry into the mine was severely damaged and communication was cut off by the so-far unexplained explosion.

For a week, there was no sign of life. Then, last Sunday, rescuers felt a pull on one of the ropes they were lowering into small shafts leading down into the dark.

A paper note was then sent up on a rope from a group of 12 surviving miners - 11 trapped in one place and a 12th trapped further below.

Since then, the contact with the 12th miner has been lost, while one of the group of 11, who had fallen into a coma after sustaining a head wound in the explosion, was on Thursday confirmed dead.

Mining accidents are not uncommon in China, where the industry safety regulations can be poorly enforced. In December last year, 23 miners died after a carbon monoxide leak at a coal mine.

In September, 16 workers were killed at another mine on the outskirts of Chongqing, also due to carbon monoxide. In December 2019, an explosion at a coal mine in Guizhou province, south-west China, killed at least 14 people.

The group of 10 known survivors are trapped in the dark some 600m (2,000ft) underground. They are in regular contact with the rescue teams.

A communication line has been established and food and medicine can be lowered to them through a narrow shaft.

While they've been receiving porridge and nutritional liquids, the miners a few days ago asked for a traditional meal of sausages.

Eight of them are thought to be doing well, while two are in poor health.