The former vice mayor and the former police chief of northern China's Datong City are under investigation for covering up coal-mine accidents, local discipline authorities said Thursday.

Zhang Xiaoya, deputy secretary of the Shanxi Provincial Committee of Discipline Inspection, said former vice mayor Wang Yanfeng and former police chief Shen Gongyuan are suspected of having taken bribes from mine owner Li Kewei.

Zhang said Wang and Shen are the highest-ranking officials disciplined after officials from the Ministry of Supervision and the State Administration of Work Safety began an investigation in December 2008 into the cover up of five coal-mine accidents that occurred in the 2002-2004 period in Datong.

Thirteen people died in three of the five accidents. None of the accidents were reported to work safety authorities.

Zhang said the sums taken as bribes could be "huge."

"Once the investigation is concluded, the discipline committee will make it public," said Zhang.

Vice mayor Wang Yanfeng was responsible for coal production in the coal-rich Datong before he was removed from his post in April.

An initial investigation suggests businessman Li Kewei owned seven coal mines in Datong. He bribed a number of officials to obtain production approval and to cover up safety risks and accidents.

The discipline committee official declined to disclose how many officials have been implicated in the case.