A landslide that killed 73 people and left four others missing in the southern city of Shenzhen on Dec 20 was an "extraordinarily serious" industrial safety accident, according to a report issued on Friday by a State Council investigative team.

After nearly seven months of studying the accident at the Hong'ao dump site, the team concluded it was caused by the improper storage of construction waste and lack of a drainage system at the landfill site.

The team identified 110 people with varying levels of responsibility for the accident. Fifty-three of them could possibly be summoned to appear, be placed under residential surveillance, be detained or arrested.

The Supreme People's Procuratorate said on Friday it had filed cases against 25 suspects.

The suspects include Meng Jinghang, former director of Shenzhen's urban management bureau, Chen Minfeng, a member of Guangming New District's Party Working Committee, and Peng ShuiQing, district director of the city's Urban Planning, Land & Resources Commission.

The investigative report recommends that Shenzhen Yixianglong, which managed the dump site, lose its licenses and company executives be banned from executive posts in the sector. Two companies held responsible for the accident should face fines and other punishments, the report said.

In addition to causing 73 deaths, the accident destroyed 33 buildings with direct economic losses at 880 million yuan ($132 million). "Landslides are a common risk at dump sites and dozens occur each year, but the size and the losses in Shenzhen's incident are very rare," a member of the investigative team said.

The team's report said the Shenzhen government neglected its management and supervisory duties, and the municipal bureaus of planning, construction, water resources, and environmental protection illegally permitted the dump site's construction.

The direct cause of the landslide was the dump's failure to build an effective drainage system, leaving the base of the waste piles saturated with water.

grace@chinadailyhk.com