CHANGSHA, CHINA (BNO NEWS) — Six miners were trapped underground after a coal gas leak in central China on Wednesday, the state-run Xinhua news agency reported.

The accident took place at noon (local time) in a 30-meter-deep shaft at the Tianxin Mining Company in Jiahe County of Hunan Province.

Three of the trapped miners were confirmed to be alive by rescue crews who contacted them through underground communication systems. According to official reports, the trapped men are gas inspectors and repairmen.

The location of three of the other miners are still unknown, and it is unclear if they are still alive.

Rescue efforts were still ongoing as of late Wednesday. A tunnel to reach the trapped men has been completed and rescuers are still looking for the three unaccounted men.

The cause of the accident is unknown and is under investigation.