ZHENGZHOU - Rescuers have retrieved four bodies from the scene of Friday's colliery explosion in central China's Henan Province, local authorities said.

Rescuers have made the site safe, after gas filled the pit in Ruzhou City around 10:37 a.m. on Friday, according to Li Yongsheng, assistant chief engineer of China Pingmei Shenma Group.

When the blast occurred, 250 miners were working more than 500 meters underground. Nine are still missing.

Rescuers are clearing the coal bed and restoring the lift system to cintinue the search, Li said.

The cause of the accident is still under investigation.