Rescuers have recovered the bodies of four miners 11 days after an unfinished coal mine collapsed in northwest China's Xinjiang Uygur Autonomous Region, the local authorities said.

The search for the remaining six missing miners was still underway, according to a statement issued by the Communist Party of China committee of the Mongolian Autonomous County of Hoboksar.

Altogether 21 workers were in the shaft when the accident happened at about 11:20 a.m. on March 30 at the Shajihai Coal Mine. Eleven were lifted safely to the ground, but 10 others were trapped.

More than 110 people have been deployed on the rescue operation, but their efforts have been hampered by the loose geological structure, frequent collapses and underground water, according to an officer with the Xinjiang coal mine work safety watchdog.

So far, rescuers have pumped out 6,570 cubic meters of water and excavated 328 cubic meters of debris after clearing 12 meters of the collapsed shaft, which is as deep as 700 meters underground.

However, rescuers have not established contact with the trapped workers or discovered any signs of life.

The Shajihai Coal Mine, owned by the Luneng Coal-Electricity Development Co. Ltd., is designed with an annual output capacity of 900,000 tonnes. Construction started in June last year and it is expected to be in operation in October next year.