Six more Chinese workers trapped in a coal mine in east China’s Shandong Province have died, taking the death toll from the accident to 19, officials said on Monday. The bodies of six workers trapped in the coal mine were found on Sunday, state-run Xinhua news agency reported, citing the rescue operations.

The accident occurred at Longyun Coal Mining Co. Ltd. in Yuncheng County on October 20.  More than 170 rescuers, including medical workers and firefighters, were dispatched to rescue the injured and search for the trapped miners.

A total of 22 workers were trapped in a 74-meter-long tunnel after coal fell at both ends from the rock burst. However, one of the workers was rescued. Rescuers have cleared 55 meters of the tunnel and are working on the remaining 19 meters to search for the last two miners who remained trapped, the report said.

In August, 13 miners were killed in a mine explosion in southern China. Rock burst accidents are often caused by fractures in rocks due to mining. Though the number of deaths has reduced at coal mines in recent years, mining accidents are common in China, the world’s largest coal producer.