Screenshot of a monitor shows rescue operations underway at the Qingshuiying coal mine in the Ningxia Hui autonomous region. (Photo: chinadaily.com.cn)

Four miners were trapped by a roof collapse in a coal mine at around 11:50 pm on Thursday at the Qingshuiying mine in the Ningxia Hui autonomous region.

As of Friday afternoon, the miners are safe and a rescue operation is underway, Ningxia's emergency management department said.

The mine belongs to Ningxia Coal of China Energy Corp.

Aerial image of the Qingshuiying coal mine in the Ningxia Hui autonomous region. (Photo: chinadaily.com.cn)

After the collapse, rescue work began immediately. Rescuers made contact with the four miners at about 8:40 am on Friday.

They are drilling and digging a passage through which the miners can escape. As of 1 pm on Friday, the rescue passage had reached 5 meters in length. It will take another 25 meters to get through, which is expected to take nearly 40 hours.