An investigation has revealed that the cause of a chemical plant explosion in April that killed three people and injured three others in Juye county of Heze, Shandong province, was stainless steel tools striking barium azide. This sensitive chemical compound can detonate from friction or intense heat.

The findings were released by the Department of Emergency Management of Shandong Province on Friday.

The accident occurred at Heze Dijade Chemical Corporation at 7:36 pm on April 22, resulting in direct economic losses of over 11 million yuan ($1.6 million).

A joint investigation team was formed to probe the incident, led by the provincial emergency management department and including officials from public security, industry and information technology, the trade union federation, and the Heze government.

The investigation found that the direct cause was an explosion triggered by impact or friction between stainless steel tools and a barium azide filter. Operators were using the tools to scrape the substance from filter cloths.

The report also stated that the company intentionally concealed the fact that workers were missing after the accident occurred.

The investigation team has recommended that four individuals, including the general manager of the company, directors of its production, safety and environmental protection, and sales departments, be held criminally liable.

Additionally, 20 other individuals, including a county deputy head, are to face disciplinary or administrative punishments for their roles.