BEIJING (AP) — Fourteen workers who were trapped when a coal mine in southwest China collapsed 10 days ago had died, media reported Sunday.

A rescue operation finished Sunday noon after the bodies of the miners were retrieved, state-owned Xinhua News Agency said.

The workers were trapped after the roof of a shaft at Sanhe Shunxun coal mine in Guizhou province collapsed on Feb. 25.

The rescue operation was challenging because the roof caved in about 3 kilometers (1.9 miles) from the entrance of the mine, and the collapsed area was considerably large, media reported.

Further investigation into the cause of the accident was underway.

China’s coal mines are among the world’s deadliest, regularly suffering explosions and gas leaks despite repeated safety crackdowns.