China's work safety authority said Wednesday that four mine owners have been found to have intentionally delayed reporting or tried to cover up deadly coal mine accidents that killed at least 18 people last month.

The cover-up attempts were reported in two coal mines in central China's Hunan Province, southwestern Guizhou Province and northern Shanxi Province, according to a statement from the State Administration of Work Safety.

The work safety watchdog vowed to severely punish those found responsible for concealing the accidents.

Regulations concerning coal mine safety state that the owners of coal mines should inform local government and work safety authorities immediately after an accident occurs.

According to the statement, a coal mine in the city of Leiyang in Hunan Province was flooded on July 4, trapping 16 miners underground.

But the accident was not reported to the local government until whistleblowers informed local work safety authorities 12 hours after the flood, which delayed the start of rescue operations and resulted in the deaths of eight miners, the statement said.

In a separate accident in Hunan, three miners were killed in a gas explosion that occurred on July 17 in a coal mine affiliated with the Hunan Province Coal Mining Group in Jiahe county.

Local government departments were informed about the mishap one day after the deadly accident, the statement said.

The owner of a coal mine in Pu'an county in Guizhou Province failed to report a tunnel collapse that occurred on July 25, trapping five miners and later 53 rescue workers underground.

Local government work safety authorities reported the incident 22 hours after it occurred, the statement said. All of the trapped people were rescued.

The managers of a coal mine belonging to Yuquan Coal Mining Co., Ltd. in the city of Yangquan in Shanxi concealed an explosion on July 26 that left seven dead and 30 others injured, the statement said, adding that the local government was unable to confirm the accident for three days due to the concealment.