BEIJING -- A subsidiary of the China Railway Tunnel Group purposefully concealed a fatal railway tunnel explosion that occurred on December 25 in north China's Shanxi Province, the State Council's Work Safety Committee said Thursday.

Eight people were killed and five were injured in the explosion, which occurred on a section of railway tunnel that was under construction, the committee said in a statement.

Authorities confirmed the explosion on December 30, one day after it was revealed online by netizens, the statement said.

An initial investigation singled out illegal blasting operations as the cause of the accident, as well as revealed that the explosion was concealed by the construction project's manager.

An investigative team has been set up to probe the accident, local authorities said.

The statement said authorities will step up crackdowns on the concealment of fatal accidents and implement greater punishments for those found responsible.

The statement also mentioned three other workplace accidents that occurred over the last week, including a platform collapse in a parking lot that was being built to support a metro line in Shanghai. The accident left five dead and 18 others injured.