A coal mine flood in central China which managers tried to cover up killed 15 people, less than a week after 21 miners died in another unreported accident, the official Xinhua agency said.
The flooding in Shangjiwu mine, in Henan province, started late on Thursday when 52 people were thought to be underground.
The mine operators organised a rescue operation themselves instead of reporting it to work safety officials, but residents of nearby Ruzhou city told police about the disaster on Friday, Xinhua said.
The small, privately-owned mine had won government approval to upgrade annual capacity to 150,000 tonnes from 90,000 tonnes and was working on the expansion at the time of the accident.
The trapped workers were killed by a high density of gas and a lack of oxygen, Xinhua quoted Li Jiucheng, director of Henan Coal Mine Safety Administration, saying.
Police are holding mine owner Wang Xianguo, have frozen the company's accounts and are hunting for two fugitive managers.
Last Sunday rescue work was delayed 44 hours after a coal mine gas owner in central Shanxi province allegedly tried to cover up a blast, Xinhua reported. Twenty-one miners were killed.
China has the world's deadliest coal mines. Last year, 4,746 workers were killed in mine blasts, floods and collapses as collieries pushed production beyond safety limits to meet demand from the booming economy.