China’s state news agency Xinhua reported high-gas density had impeded the search for the 57 miners trapped when the flood occurred.

Seven miners died and a total of 21 miners escaped or were rescued, leaving 29 trapped without contact when their mine flooded Monday.

Rescuers located the trapped miners’ work area last Wednesday but rain and high-gas density have slowed the effort.

More than 2000 people have been involved in the rescue.

The mine has an estimated reserve of 2.98 million tonnes of coal. It has been producing 190,000t a year and was reported to be fully certified for operation.