In this photo released by Xinhua News Agency, a miner receives medical treatment after being rescued from the Jilinqiao coal mine in Huangfengqiao Township, Youxian county, central China's Hunan province, Monday, May 8, 2017. A gas leak in the coal mine killed more than a dozen people, local authorities said Monday. (Li Ga/Xinhua via AP)

The leak happened on Sunday morning when miners were working in the shaft of the mine in Youxian county in Hunan province, according to a statement from the propaganda department of the Communist Party committee of Zhuzhou city, which administers the area.

Rescuers managed to bring to safety 37 miners who are receiving hospital treatment, it said.

The official Xinhua News Agency said that police had detained unspecified people pending an investigation.

China is the world's largest producer and consumer of coal. Its mining industry has long been one of the world's deadliest, with hundreds of deaths annually, even as China has tried to improve standards by shutting older, smaller mines.