GUIYANG, July 2  -- Four people have been killed and another four injured in the collapse of a high-speed railway tunnel under construction in southwest China's Guizhou Province.

Rescue efforts ended on Wednesday for the workers trapped by the Dadu Mountain tunnel cave-in, which occurred at 11 a.m. on Tuesday, said the provincial work safety administration.

The tunnel belongs to the high-speed railway line linking east China's business hub of Shanghai and Kunming, capital of southwest China's Yunnan Province.

The four injured workers have been taken to a local hospital and their lives are not in danger.

The cause of the accident is being investigated.