XIAN - Death toll in a coal mine accident in Northwest China's Shaanxi province on Wednesday has risen to seven, and rescue of six trapped workers is under way, local authorities said Thursday.

As of 9 am Thursday, rescuers had found the bodies of five of the 11 trapped workers, bringing the death toll to seven.

The accident occurred around 11 am Wednesday at a coal mine under construction by China National Coal Group Corp in Yulin City .

An initial investigation showed that the accident happened at a shaft when the cement pipe fell off.

Thirty-seven workers were working under the ground, and 26 were lifted out. The injured have been sent to local hospitals, and two of them died later after treatment failed.

Further investigation into the accident is under way.