The Department of Emergency Management of Guangdong Province has released a report into the "Dec 4" collapse on the Shenzhen-Jiangmen railway line which concluded that the deadly accident was caused by the contractor violating regulations during tunneling.

The collapse at the construction site of section 5 of the new Shenzhen-Jiangmen railway line in Shenzhen on Dec 4 last year resulted in 13 deaths and direct financial losses of approximately 72.61 million yuan ($10.22 million).

On Monday, the findings of the provincial government's accident investigation team were released, concluding that the incident was caused by construction units violating regulations during tunneling, which led to partial collapse above the tunnel face. Ineffective engineering measures during abnormal conditions resulted in ground subsidence, workers falling along with the collapsing ground and, ultimately, fatalities, according to the Xinhua News Agency.

The investigation concluded that the direct cause of the accident was the contractor's failure to halt excavation or enhance support when tunneling reached geologically unstable sections. This led to repeated collapses at the tunnel face, and inadequate emergency response ultimately led to ground subsidence and casualties.

The investigation further found that no relevant unit adequately fulfilled their responsibilities, with the construction, project management, design and supervision entities all demonstrating lapses in risk management, emergency response and on-site management. In addition, safety supervision and industry regulatory bodies failed to fully exercise their oversight and regulatory duties.

The responsible units will face administrative penalties and internal accountability measures, while evidence of suspected dereliction of duty by relevant personnel has been transferred to disciplinary inspection and supervisory authorities.