A rescue operation to save 29 trapped miners from a flooded iron ore mine in north China has hit new difficulties, a rescue official said on Monday.

Problems appeared on the sixth day of the operation as the underground water level had risen 10 meters since Saturday due to a slurry flow and subsidence.

As the hydraulic pressure rose, large amounts of slurry and water could flood the tunnels, threatening the lives of rescuers, said experts in the rescue team.

The operation resumed on Sunday morning and residents near the mine in Inner Mongolia Autonomous Region had been relocated to safe areas.

Rescuers have been drilling a hole with a diameter of 30 cm to the No. 3 shaft, through which they hope to deliver oxygen and food to the trapped miners, who are believed to still have a chance of survival.

The operation has become extremely delicate as they try to avoid more slurry flows or sudden rises in the water level.

Rescuers stopped pumping water and dredging silt from the No. 2 shaft early on Saturday due to a sudden rise in the water level. Fifty-one rescuers were evacuated from the shaft.

The flood occurred in the early hours of Wednesday at Haolaigou Iron Ore Mine in Donghe District of Baotou, when 46 miners were changing shifts. Only 11 miners escaped, according to rescue headquarters.

Six of the 35 trapped miners were rescued on Thursday and are recovering in Baotou Central Hospital.

After the accident, all mines in Baotou were ordered to suspend operations until "they were proved legal and safe after a thorough examination".

Police are keeping Cao Shihu, legal representative of Chaoyue Mining Co. Ltd of Baotou City, which owns Haolaigou Iron Ore Mine, under surveillance.

With more than 100 employees, Chaoyue Mining is a private company set up in 2001. Its mines have a production capacity of 100,000 tons of iron ore concentrate a year.

The cause of the flooding remains unclear.

Inner Mongolia reported more than 84 mine accidents last year, including 23 coal mine accidents, and 124 deaths of miners, according to the regional work safety administration.

Zhao Shuanglian, deputy chairman of the region, said the local government would step up efforts to improve qualifications of miners, eliminate outdated mining facilities and close unsafe mines.

(Xinhua News Agency January 23, 2007)