CHANGSHA, Dec. 18 (Xinhua) -- Six people were killed, one injured and another left missing in a coal mine explosion in central China's Hunan Province, local work safety watchdog said early Tuesday.

The blast occurred around 3 p.m. Monday at Niulanchu Coal Mine in Zhongfang County, according to work safety authorities in Huaihua City, which administers Zhongfang County.

Six miners died on the spot and one was injured seriously and sent to a local hospital.

Rescuers are still searching for one more miner who went missing after the blast, authorities said.

An initial investigation showed that mal-operation were to blame for the blast.

The mine, with an annual capacity of 40,000 tonnes, has completed a technical improvement in April.

A further investigation into the cause of the accident is under way.