Zhao Jianxi, Party secretary of Xiaoyi, Shanxi province, and Yang Guang, the city's mayor, were removed from office on Friday following a flooding accident at an illegal coal mine.

The mine in the village of Duxigou was flooded at about 11pm on Wednesday, trapping 22 people underground, with four escaping to safety. A total of 20 of the trapped miners had been rescued as of 7 pm on Friday while two others were found dead, according to the Ministry of Emergency Management.

Local police said they have offered a reward of up to 100,000 yuan ($15,673) for information leading to the arrest of the mine's owner, Du Jijiang, who remains at large.

Public security authorities at the provincial, municipal and county levels have sent 350 police to the area to investigate the accident and maintain order. At least seven people involved in the operation of the illegal coal mine have been detained.

As of Friday morning, eight rescue teams of more than 400 people had been involved in rescue work. From 10:05 am on Thursday to 6 am on Friday, 3,100 cubic meters of water had been pumped out of the mine and the water level had dropped by 2.1 meters, the local government said in a statement.

It said the site of the illegal coal mine was "extremely secretive". A wall had been built around the mine to conceal it, and a hidden channel of more than 170 meters equipped with conveyor belts had been excavated. The exit of the channel was concealed with steel plates covered with dirt and weeds and could only be opened by hydraulic tools.

Lin Wu, Party secretary of Shanxi province, said during a teleconference on Thursday evening that the case has had an "extremely bad" impact and exposed problems in relation to supervision, responsibilities and the implementation of measures in the crackdown on illegal mining and illegal production, Shanxi Daily reported.

He said any act of collusion between government and business, as well as deals involving power and money, should be investigated thoroughly and severely punished.

Sun Ruisheng in Taiyuan contributed to this story.