China on Friday quietly released the findings of an inquiry into its worst industrial accident in years, calling for 123 people connected to the deadly chemical blast to be punished.

The report followed an investigation by the State Council evaluating the cause of the August blast in the northern city of Tianjin that left at least 165 dead.

Industrial accidents are common in China where safety standards are often lax, but the massive blast sparked widespread anger over a perceived lack of transparency by officials about its causes and environmental impact.

The report appeared on the web site of the State Administration of Work Safety just as the country prepared for a days-long national holiday for Chinese New Year, when there is often a lull in media coverage.

The blast, which caused over $1 billion in damages, was caused by improper chemical storage by Tianjin Ruihai International Logistics, the document said.

Dry weather conditions allowed for the spontaneous combustion of "nitro-cotton", a flammable compound stored in the warehouse, it said. The fire then ignited other chemicals, including ammonium nitrate, a highly explosive compound commonly used in fertiliser and also in homemade bombs.

But the underlying cause was that government bodies in charge of the port, up to the ministerial level, routinely ignored or violated laws and regulations regarding chemical storage, according to the report.

It added that some officials connected to the explosion were guilty of "corruption" and "abuse of power" and recommended the 123 people, including five at the ministerial level, face disciplinary action.

Another 49 had already faced legal proceedings, it said.

Thousands of tonnes of hazardous chemicals were stored at the warehouse, some 600 metres (2000 feet) from residential buildings. Chinese regulations say hazardous materials should be stored at least 1,000 metres away from homes.

The blast released clouds of toxic chemicals into the air and created a large pool of contaminated water, and the report recommended continued monitoring of long-term health and environmental damage.

A spate of industrial accidents in recent years has raised concerns about the enforcement of residential zoning regulations, government transparency and adequacy of firefighter training in China.

On social media, some chided the report's recommendations.

"How could no one get the death penalty?", one commenter wrote. "So many people died!"