Four people detained after a March 9 coal mine accident in which six workers died were formally arrested Thursday in Jungar Banner, Inner Mongolia Autonomous Region, prosecutors said Friday.

The four were identified as Dan Hongyu, owner of the Luxinju Coal Mine; He Ping, deputy director of production; Wang Yaozhong, chief of the team hired to tunnel an underground passage, and Liu Penghui, contractor of the excavation project.

They will be charged with negligence causing a serious accident, the Jungar Banner People's Procuratorate said. The starting date of the trial hasn't been announced.

Yuan Fucheng, the mine's deputy safety director, and safety inspector Jin Xifu, who were also detained two days after the accident, have been released on bail for lack of evidence.

The accident happened on the night of March 9 in Luxinju Coal Mine, a privately-owned, licensed venture based in Jungar Banner, Ordos City, as a dozen miners worked underground.

The prosecutor's office said its investigators determined that the mine was ordered to suspend production in December for safety improvements. But owner Dan Hongyu met on Feb. 22 with Liu, whom he asked to hire staff for the tunneling project.

The mine resumed operations on March 1 without official approval.

The untrained miners, who were attempting to speed up work, broke the seal on an old shaft when no ventilation equipment was operating, allowing carbon monoxide to flood the facility.

The prosecutor said Wang, the excavation team leader, had asked He to turn off the ventilation equipment.

Six of the miners were killed by the toxic gas, while the other six were slightly injured.

(Xinhua News Agency April 17, 2009)