QIXIA:Workers trapped in a gold mine in China since Jan. 10 may have to wait another 15 days before they can be rescued because of a blockage on their intended escape route, officials said on Thursday.

A total of 22 workers were trapped underground after an explosion at the Hushan mine in Qixia, a major gold-producing region under the administration of Yantai in Shandong province on the northeast coast.

One is confirmed to have died, while 11 are known to be alive. The remaining 10 are missing.

Rescuers were drilling new shafts on Thursday to reach 10 of the men in the middle section of the mine, more than 600 metres from the entrance, who have been sent food and medical supplies. Another survivor has been found in a different section.

The shafts include one 711-mm (28-inch) diameter shaft that rescuers hope to use to bring the survivors to safety.

However, at least another 15 days may be needed to clear obstacles, Gong Haitao, deputy head of Yantai's propaganda department, told a news conference at the headquarters of the rescue operation.

A "severe blockage" 350 metres down was much worse than feared, officials said, adding that it was about 100 metres thick and weights some 70 tonnes.

Thick smog, reeking of chemicals, hung over the muddy road leading up to the mine site and a row of ambulances on standby in a carpark, reducing visibility to a few hundred metres.

Police have sealed off the road to the mine, cutting through muddy apple orchards and warehouses, to ensure rescue efforts are not hampered. Health workers in white protective gear took temperatures beside mounded earth and tents as part of COVID-19 precautions.

About 600 people are involved in the rescue, with as many as 25 ambulances waiting at the scene, as well as neurosurgeons, trauma specialists and psychologists.

A Reuters team saw fire trucks and cars coming and going through a checkpoint on an approach road.

China's mines are among the world's deadliest. It has recorded 573 mine-related deaths in 2020, according to the National Mine Safety Administration.