BEIJING, China:  An early investigation into China's worst mining disaster in more than 15 years has found hidden tunnels, missing tracking devices, and fake doors. State media said the government has promised a full and thorough inquiry.

At least 82 people died in a gas explosion late on May 22 at the Liushenyu coal mine in Shanxi province in northern China. Two people are still missing, and 128 others were taken to the hospital. This is the deadliest mining accident in China since 2009, when a similar explosion killed 108 people.

The exact cause of the blast is still being investigated. However, reports say the mine had secret tunnels and fake maps, and employed unregistered contract workers who were not given the required tracking devices. These issues likely made the disaster worse.

The company running the mine reportedly kept two sets of plans—one real and one fake for inspectors. Some mining areas were hidden from the authorities. The coal taken from these secret tunnels was not recorded or taxed.

Workers also built fake doors from wire mesh and plastic sacks, then covered them with mortar to resemble real tunnel walls. When inspectors arrived, workers were warned and quickly closed these doors, covering them with coal dust to hide them.

To avoid detection, the company hired subcontracted workers for the hidden tunnels without proper records or tracking devices. Official records showed only 124 workers underground during the blast, but actually 247 were there, meaning 123 workers were untracked.

Because of missing maps and tracking information, rescue efforts have been very difficult. The mine, already considered high-risk for gas explosions, had also avoided installing proper gas monitoring systems.

Authorities were aware of some problems earlier. In 2025, the mine was fined for concealing work areas, but the penalty did not deter illegal activities.

After the accident, some coal mines across China have stopped or reduced production to carry out safety checks.