Fifteen workers died after an explosion at a coal mine in northeast China, state media reported on Monday.

The blast occurred on Sunday afternoon at a legally run mine in Qitaihe city, Heilongjiang province, according to the Xinhua news agency, which said the cause of the accident was still being investigated.

Twenty-five workers were in the mine when the explosion happened, with 10 managing to escape. The bodies of the 15 killed were recovered on Monday, Xinhua reported.

Nearly 3,800 people died in Chinese coal mines last year, according to official figures. However, independent monitors say the real figure is much higher as many accidents are covered up.