BEIJING (AP) — China says a railway company covered up a tunnel explosion that killed eight people and injured five last month.

The State Administration of Work Safety says a subsidiary of state-owned China Railway Tunnel Group concealed the Dec. 25 explosion in northern Shanxi province in a railway tunnel under construction.

A statement posted on the agency’s website Thursday says people reported the explosion to authorities Sunday. It called the cover-up “vile.”

The official Xinhua News Agency says the blast was revealed online.

Xinhua says an initial investigation found that the accident was caused by illegal blasting operations and concealed by the construction project’s manager.

The work safety administration says authorities will crack down on the concealment of fatal accidents and mete out severe punishments. It did not specify the punishments.