The death toll in a central China mine blast last week has risen to 28 and about 16 people were believed still trapped underground, local authorities said on Monday.

Rescuers found the bodies of eight trapped miners on Sunday, said a spokesman with the rescue headquarters.

Another body was found under the debris of a collapsed buildings on the surface of the mine, he added.

Investigations so far showed that the blast killed 23 miners underground and five on the surface. Another two on the surface were injured. Sixteen people were still trapped underground, the spokesman said.

More than 500 rescuers were searching for the trapped miners, he said.

About 90 miners were working underground when the gas explosion occurred at 7:20 p.m. on March 31 in a coal pit privately owned by Guomin Mining Co., Ltd., in Yichuan County, Luoyang City in Henan Province.

The rescue headquarters said 51 miners survived the explosion. Of them, 31 were saved by rescuers and 20 others escaped by themselves.

Work safety authorities ordered the mine to suspend operations after a gas outburst on May 1, 2009, and production after that date was illegal, said a statement from the Henan Administration of Work Safety.

The coal mine was under technological renovation and was designed to have an annual production capacity of 150,000 tonnes.

Yichuan County Chief Wu Ligang and three other county officials have been removed from their posts since the accident.