An investigation report into a safety incident that led to the deaths of six people at a China National Gold Group plant in the Inner Mongolia autonomous region has revealed the cause of the accident and recommended 42 individuals be held accountable, according to the regional emergency management department.

The incident occurred on July 23 at a plant in Hulunbuir, killing six people and injuring one other person.

According to the official report, released on Saturday, 55 students and teachers from Northeastern University in Shenyang, Liaoning province, were visiting the plant to observe flotation processes as part of a field study program. Seven people — one teacher and six students — fell into a flotation tank and drowned in slurry after a steel grating they were standing on collapsed.

Investigators identified the direct cause as an undersized grating plate that had been improperly welded to support beams. Severe corrosion in the humid environment, combined with the group gathering off the designated safe walkway, caused the overloaded weld to fail. The six people asphyxiated in the slurry, the report said, ruling out poisoning, burns or mechanical injuries.

The investigation found widespread management failures, including chaotic on-site safety oversight, flawed safety protocols, superficial hazard inspections and irregular management during the plant's construction.

Following the accident, the Inner Mongolia regional government launched an upgraded investigation involving expert participation, while the regional commission for discipline inspection pursued a parallel accountability probe.

The report recommended accountability for 42 people. Four employees of China Gold Inner Mongolia Mining Co, suspected of criminal offenses, have been transferred to judicial authorities, and public security organs have imposed criminal compulsory measures against them.

The former head of the emergency management department of Xin Barga Right Banner has been expelled from the Communist Party of China and dismissed from public office, with suspected criminal issues transferred for further review and prosecution.

Separately, an investigation report into a major restaurant fire in Liaoyang, Northeast China's Liaoning province, was released on Sunday by the provincial department of emergency management, identifying the incident as a serious workplace safety accident involving multiple violations and regulatory failures.

The fire broke out at about 12:20 pm on April 29, at the Sanli Chuniang restaurant in Baita district, killing 22 people and injuring three others.

According to the report, the blaze was directly caused by a still-lit cigarette butt discarded by a customer surnamed Wang. Fanned by the wind, the cigarette butt rolled through a gap beneath an exhaust duct installed close to the building's exterior wall and entered an inspection opening, where it ignited combustible waste, including cardboard boxes that had been illegally stored.

The fire spread rapidly as aluminum-plastic composite panels used in the restaurant's exterior decoration and polystyrene insulation materials on the outer wall caught fire, investigators said.

The accident was attributed to the restaurant's failure to fulfill its safety responsibilities, as well as inadequate oversight by local authorities and relevant departments. The report recommended transferring eight individuals to judicial authorities and said 40 public officials will be held accountable following a disciplinary investigation by provincial anti-graft authorities.