HEFEI -- Four people died and two were injured after two cave-ins at a sewer construction site in east China's Anhui Province on Wednesday.

The first collapse happened at about 3:00 p.m. at the site in Taohua Township of Feixi County, burying one worker, witnesses said.

When other workers attempted to pull him out, another cave-in occurred, burying six altogether.

By 7:00 p.m., all the workers had been rescued and sent to hospital, but four of them died after emergency treatment failed, a county government spokesman said.

The other two workers are still being treated and the cause of the accident is being investigated, the spokesman said.