XI'AN, Jan. 13 (Xinhua) -- The death toll in a coal mine roof collapse in northwest China's Shaanxi Province has risen to 21, as rescuers found another two trapped miners dead Sunday morning.

The accident happened around 4:30 p.m. Saturday at the Lijiagou coal mine of the Baiji Mining Co. Ltd. in the city of Shenmu.

At that time, 87 people were working underground. Sixty-six of them were lifted to safety after the accident. An investigation into the cause of the accident is underway.