Sixteen people were trapped underground after a coal mine flood in Hunan province, local authorities said Thursday.

The accident happened at 6 p.m. Wednesday when 40 workers were underground, 24 of whom escaped while another 16 were trapped in a licensed Qielichong coal mine in Sandu town in Leiyang city, a municipal government official said.

The coal mine official reported the accident to the municipal government at 6:30 a.m. Thursday, and four teams of rescuers were sent to site, the official said.

Rescuers went underground every six hours to rescue the trapped people but as of 10:30 p.m., all the 16 were still trapped, the official said.