XI'AN - At least 18 people were still trapped underground after a roof collapsed in a colliery in northwest China's Shaanxi Province late on Thursday, according to local authorities.

The accident occurred at around 7 pm at Ruifeng Coal Mine, a facility in Yulin city of Fugu county with an annual capacity of 1.5 million tonnes, said an official of the Yulin city government.

As of 9:40 pm, two people had been rescued while at least another 18 were still trapped underground, the official said.

Rescuers said the situation underground is not yet known.