The country's top work safety watchdog on Thursday condemned a subsidiary of a State-owned enterprise which tried to cover up a deadly explosion at a railway tunnel project in North China and called for heavier punishment for such violations.

The explosion, which killed eight people and injured five, occurred around about 2:40 pm on Dec 25 when the workers were setting explosives in a tunnel under construction in Shanxi province, according to the Work Safety Committee of the State Council.

Workers stand in silent tribute on Tuesday to the eight people killed in a railway tunnel project explosion in Shanxi province. [Photo/Xinhua]

The accident was caused by illegal blasting operations, according to an initial investigation by the Shanxi provincial government, the statement said.

However, the construction company, a subsidiary of the China Railway Tunnel Group, did not report the accident to the government until it was exposed by netizens and confirmed by the government five days later on Dec 30.

"It (the covering up) is a very serious violation," the committee said, adding that heavier punishment should be handed down to organizations and individuals that deliberately conceal work safety accidents.

China Railway Tunnel Group is China's largest corporation for tunnel and underground projects.

Li Xiaopeng, acting governor of Shanxi province, said he felt very angry and shocked at the SOE's concealment of the fatal accident. Li and some other officials stood in silent tribute to the dead during a meeting on Tuesday, according to Shanxi Daily.

Four managers in charge of the construction project have been detained by police on allegations of not reporting work safety accidents, the Shanxi provincial public security department said on Tuesday.

To conceal the accident, the company sent some of the injured workers to a hospital in Mengzhou in Henan province, which is more than 360 km from Puxian county of Shanxi province where the accident occurred, Xinhua News Agency reported.

Tang Fu, 26, a worker from Sichuan province, said that he was driving a forklift in the tunnel when the explosion with the power of 120 kg of TNT occurred.

"I fainted after hearing a 'bang', and when I woke up, my right eye was lost," he was quoted as saying by Xinhua.

Zhao Dejun, a 48-year-old worker from Sichuan province, suffered serious injuries to his spine and hipbone, and also lost hearing in the accident, Xinhua reported.

Li Guoli, vice-chairman of the labor union of an SOE subsidiary in Shanxi province, said that some SOEs contracted out their projects to unqualified private companies, which increases safety risks.

Apart from the explosion, three other workplace accidents that occurred last week were also mentioned in the statement made by the State Council's Work Safety Committee.

A chemical factory in East China's Anhui province caught fire on the night of Dec 28, leaving the factory's production facilities partly destroyed. Even though there were no casualties, the accident was of great concern to the public since the factory is located in a densely populated region, the statement said.

In another case, the work platform of a subway project in Shanghai collapsed on Dec 31, killing five workers.

Three firefighters also died when they tried to put out a fire in a company at Xiaoshan district of Hangzhou, Zhejiang province, on Tuesday morning, the statement said.

Work safety authorities will crack down on the concealment of fatal accidents and harshly punish those found responsible, the committee said.

Contact the writer at anbaijie@chinadaily.com.cn