Forty-three people have been held accountable for a fatal transportation accident that happened at a coal mine in Jixi, Heilongjiang province, in December 2023, according to an investigation report released on Thursday.

The accident occurred at Kunyuan Coal Mine in Jixi's Hengshan district at 2:36 pm on Dec 20, 2023, when a train of five mine cars carrying 31 workers fell down in an inclined shaft, killing 12 people and injuring 13.

It led to a direct economic loss of more than 27.3 million yuan ($3.7 million), according to the report released by the Heilongjiang Bureau of the National Mine Safety Administration.

The investigation team from the Heilongjiang provincial government found that illegal mining operations, unauthorized use of lifting equipment, and workers violating boarding procedures caused the accident.

Under concealment measures, the private coal mine illegally extracted coal in its No 3 mining area, the report said. After completing the mining work, the workers rode the mine cars to ascend a 20-degree, 600-meter-long inclined shaft. But the steel rope lifting the cars broke before reaching the entrance. Seven workers immediately jumped to escape, while the remaining 24 fell with the cars.

The investigation shows that the coal mine violated safety regulations by using winches and steel ropes not designed for inclined shaft lifting and arranging works to ride in mine cars loaded with both cargo and people.

Investigators also found evidence of the coal mine's deliberate cover-up for the accident.

After the incident, the coal mine didn't activate the emergency response mechanism as required. Without asking the professional rescue team it had signed an agreement with to participate, the coal mine just took the rescue operation by itself. None of the mine's own part-time rescue team members had underground work experience, the report said.

The on-site rescue was not standardized, and the emergency supplies were insufficient, it said.

Without reporting the incident to relevant authorities, the coal mine took a series of measures to conceal the accident, including transferring and hiding the bodies, destroying surveillance and attendance records, and falsifying the accident scene in the No 1 mining area, according to the report.

The investigation team has proposed punishments for 43 responsible individuals and relevant entities, while the Heilongjiang provincial commission for discipline inspection and commission of supervision have raised accountability opinions for supervised officials and Party members.

Fourteen of those responsible individuals, including the coal mine's actual controller and its manager, as well as the director and deputy directors of Hengshan district's coal mine administration bureau, have been subject to a criminal investigation by public security and disciplinary inspection authorities. They will also face Party disciplinary and administrative sanctions upon conclusion of legal procedures, the report said.

The other 29 have been recommended for Party disciplinary actions and administrative punishments, it said.