GUILIN -- A lack of oxygen killed seven people in the tunnel of an abandoned tungsten ore mine in south China's Guangxi Zhuang autonomous region Tuesday, local authorities said.

The accident happened at about 3 p.m. at the mine in Daxijiang township of Quanzhou county, the county government announced in a statement.

It was not immediately known why the seven people, whose identities have yet to be confirmed, entered the abandoned mine, the statement said.

Police are investigating the accident, it said.