Rescue workers are searching for nine miners reported missing after a gas leak in a coal mine in central China's Hunan Province early Wednesday.

The incident occurred at around 9:00 a.m. in the Xincheng Coal Mine of Leiyang City. Eight miners had been rescued from the mine by 12:30 p.m., said Li Ming, deputy mayor of Leiyang City.

Preliminary investigations showed nine miners were still trapped underground, Li said.

The cause of the leak is being investigated.

The privately-owned coal mine produces 30,000 tons of coal annually.