Problems mounted for rescuers searching for survivors in a flooded China mine yesterday, with officials warning of a toxic gas build-up as the death toll rose to seven.

Cramped conditions and the risk of a gas explosion in the Wangjialing mine in north China's Shanxi province have complicated efforts to find 31 workers still believed trapped in the pit, with some emergency personnel falling ill.

So far, 115 workers have been pulled to safety after more than a week trapped in the mine, in what officials have described as a "miracle" for an industry plagued by deadly accidents and a poor safety record.

Seven bodies have been recovered, the rescue headquarters announced early yesterday, but authorities say there is still hope for those trapped, even though they are believed to be in the deepest part of the state-owned mine.

"The work at the mine is continuing. We are doubling our efforts so we do not waste time," Liu Dezheng, vice-director of the Shanxi work safety administration, told reporters at a news briefing.

State-run Xinhua news agency quoted a rescue official saying teams were inching towards the last two work platforms underground. One was cut off by a submerged stretch 700 metres long and the other by a 300-metre span.

The rescue on Monday of more than 100 workers - some of whom had survived on tree bark, sawdust, paper and even coal - buoyed hopes of finding more.

But Mr Liu said workers were having trouble operating drainage pumps in the tight mine shaft, while Xinhua said toxic gas had reached "dangerous" levels in some areas.

AFP reporters have so far not been allowed into hospitals in the nearby city of Hejin to question survivors. Relatives were also being kept away, with doctors saying their patients need rest.

Reports said the workers were generally in stable condition but some suffered from psychological trauma.

Yesterday, AFP reporters also were prevented from entering a hotel 80 kilometres from the mine, where relatives of missing workers were reportedly ordered to stay.

Some anxious relatives are demanding information about their missing loved ones. "They wouldn't tell us anything, they wouldn't let us in," 46-year-old Xiang Qinghe, whose nephew was in the mine, said.

"I just want to see if he's there - if we see him, we can relax."

The accident occurred on March 28 when workers apparently dug into an older adjacent mine that had been shut down and filled with water, a practice used to stabilise the geology in abandoned collieries, press reports have said.

The government has blamed the accident on owner Huajin Coking Coal Company's failure to heed repeated warnings of an impending flood.

Safety standards are widely flouted in China's mines in the rush to meet surging coal demand - source of about 70 per cent of the country's energy.

In a commentary, the state-run English-language Global Times yesterday said if the same effort in rescue work had been applied to safety practices, "many similar accidents might well have been avoided in the first place."

More than 2,600 miners were killed last year, according to government figures, although labour activists say the actual numbers are likely far higher.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.