Police have detained 21 people suspected of trying to cover up the death toll from a coal mine accident.

Ten miners were killed and another remains missing after a flood on Friday at an illegal coal mine in Changzhi, Shanxi province.

The owner of the Shanfu Coal Mine originally told authorities that nine workers were trapped.

However, police later discovered that 11 workers were in the shaft when it was flooded with 2,500 cubic meters of water at about 1 am.

About 30 professional rescue workers were sent to the scene, along with nine ambulances and 200 technicians. All of the water had been pumped out of the shaft by 8 pm on Saturday.

The mine's owner and its manager were among those detained, and authorities froze the company's assets.

An official at the State Administration of Work Safety, who declined to be identified, said that under the regulations, concealing an accident that claims the lives of 10 people is punishable with a fine of 5 million yuan ($76,000) and up to seven years in prison.

The administration said the mine did not have a valid production license.

Authorities were unable to confirm whether the mine was private or State-owned when asked by China Daily.

In a separate flooding incident in Henan province on Saturday, five miners were killed and six others remain missing.

The accident happened at 4 pm at a mine owned by Yulongyuantong Coal Mining Corp in Pingdingshan.

Authorities said 53 miners were working in the mine at the time and 42 managed to escape.

On Sunday night, rescuers were still pumping water from the mine and searching for the trapped miners.

According to the work safety administration, the flooding was caused when water flowed in from an abandoned pit. In this case, the mine was licensed.

Wang Shuhe, deputy director of the State Administration of Coal Mine Safety, led a specialized emergency rescue team to the site and supervised the rescue.

Yulongyuantong Coal is a subsidiary of the Henan Provincial Coal Seam Gas Development and Utilization Co, a large energy enterprise owned by the Henan government.

According to reports, 1,973 miners were killed in 1,201 coal mine accidents in China in 2011, with 1,391 of the deaths in small mines.