JINCHENG -- The bodies of 20 miners have been recovered after a gas explosion in a coal mine in north China's Shanxi Province, rescuers confirmed on Thursday morning.

The blast occurred at 6:30 p.m. Sunday at Miaojiang Coal Mine, in Chengqu District of Jincheng City, Shanxi Province, when 21 miners were working underground. One of the miners remains missing.

Rescue work was delayed 44 hours because the mine owner allegedly attempted to cover up the accident.

The provincial bureau of work safety started investigating the accident on Tuesday.

Eleven people, including pit owner Wang Junjun, the contractor, the district work safety inspector and the official in charge of monitoring gas density, have been arrested for allegedly attempting to cover up the accident. Police are searching for another three people in connection with the allegation, said sources with rescue headquarters.

Ji Jianlong and Meng Shuangzhai, two Communist party officials in the village where the coal mine is located, have been dismissed in connection with the allegations of a cover-up. Li Xulong, a vice head of the district, who has already been expelled from the district Party committee, is also facing removal from office, said the city authorities.

The underground shafts were very complex and when the accident occurred the pit temperature reached 40 degrees Celsius and the gas density was 3.5 percent, said rescuers.