The fire that led to 39 deaths and nine injuries at a complex building in Jialeyuan community in Xinyu, Jiangxi province, on Jan 24 was caused by illegal construction of a cold storage facility in its basement, according to an investigation report released on Saturday.

Polyurethane foam sealant was used during construction at the first floor underground, releasing flammable gases that accumulated to reach combustible conditions. While laying plastic film on extruded polystyrene boards, static electricity was generated, igniting the gases, the foam and other flammable materials. It created a large amount of toxic smoke, according to the report approved by an executive meeting of the State Council.

The smoke quickly spread to the second floor as the fire separation in the shared evacuation staircase between the basement and the ground floor was missing. On the second floor, students and teachers were having classes organized by a training institute. Because of the security nets and advertising boards outside the classrooms, they failed to escape on time, resulting in an increase in casualties.

The accident, which happened in the afternoon of Jan 24 caused a direct economic loss of more than 43.52 million yuan ($6.17 million).

An investigation team was established by the Ministry of Emergency Management, the Ministry of Public Security, the National Fire and Rescue Administration, the All-China Federation of Trade Unions, and the Jiangxi Provincial People's Government afterwards.

The team found that the owner of the building illegally rented the basement floor, where construction of the cold storage facility was illegal. The building had significant deficiencies in fire prevention. The educational training institute and a hotel were operating in violation of regulations. The relevant local authorities failed to carry out supervision.

In an interview with Xinhua News Agency, the team suggested enhancing safety management of cold storages by regulating planning, site selection and on-site construction. It also asked for strengthened management of major places where multiple businesses operate.

Efforts should be made to promote installation of "one-click alarm" devices in crowded areas and near evacuation routes, enabling a single press to trigger building-wide alarms and prompt responses from all occupants, it said.

It also addresses issues such as congested safety evacuation routes, poorly maintained fire safety facilities, inadequate safety exits, and potential hazards such as unauthorized security nets and advertisement boards.