Courts in Yancheng, Jiangsu province, on Monday sentenced 53 people to prison over a chemical plant explosion that claimed 78 lives and seriously injured 76 in March last year.

The explosion took place on March 21 at the Jiangsu Tianjiayi Chemical Company, located in a chemical industrial park in Yancheng's Xiangshui county. It also caused the hospitalization of 640 people and an economic loss of nearly 2 billion yuan ($302 million).

The Yancheng Intermediate People's Court and seven county-level courts in the city sentenced the 53 suspects involved in 22 criminal cases.

According to the courts, Tianjiayi, whose production license had been revoked after the blast, had illegally stored dangerous nitration waste in the warehouse for a long time. The waste ignited spontaneously due to accumulated heat and caused the blast.

The company's neglect of the country's environmental protection and safety production laws, along with its chaotic management practices, also contributed to the disaster, the courts said.

They also said Tianjiayi illegally burned hazardous waste, seriously polluting the environment, and that Zhang Qinyue, the company's former general manager, should also bear criminal responsibility for bribing government officials.

Zhang was sentenced to 20 years in prison and five years' deprivation of political rights, and he must pay a fine of 1.55 million yuan for illegally storing dangerous substances, polluting the environment and bribery.

Nijiaxiang Group, Tianjiayi's holding company, also committed illegal acts, the courts said. To make profits, Nijiaxiang approved Tianjiayi's production of chemicals even though it knew that Tianjiayi's technologies and equipment did not meet national standards.

It also did not strengthen management, nor did it give proper disposal plans for Tianjiayi to store the large amount of waste, the courts said.

Nijiaxiang was fined 20 million yuan for illegally storing dangerous substances. Wu Yuezhong and Ni Chengliang, the former and current presidents of the group, were sentenced to 12 and 13 years behind bars, respectively.

Other Tianjiayi leaders, including the company's deputy general manager and its safety director, were also sentenced to prison.

Moreover, the courts said that six agencies, including Yancheng environmental monitoring center, issued false documents to avoid exposing Tianjiayi's illegal acts and interfered with the government's safety supervision.

Twenty-two people from the six agencies were sentenced from nine months to four years for providing false documents or issuing false certificates.

Some governmental departments, including the Yancheng environmental protection bureau and Xiangshui's emergency management department, should take responsibility for their serious lack of supervision and dereliction of duty, the courts said.

Fifteen government workers－including Sun Feng, former director of Xiangshui emergency management bureau－were sentenced to terms of three years and three months to seven years and six months for dereliction of duty and bribery.

After the State Council said in November last year that the explosion was a major work safety accident, some senior provincial officials in Jiangsu were held responsible for the blast, including Fan Jinlong, executive vice-governor of the province in charge of work safety, and Fei Gaoyun, the vice-governor who assists Fan in work safety management.

Fan received a disciplinary warning within the Party, and Fei was given a demerit for dereliction of duty.