Two coal miners who were trapped during work on Wednesday in Tangshan, Hebei province, were successfully brought to the surface with stable vital signs at around 10:40 am on Thursday while rescue operations were still underway for the remaining four trapped miners, according to a report by China Media Group near 11 am on Thursday.

Six coal mine workers became trapped after a collapse occurred as they worked at the Qianjiaying Mining Branch of Kailuan Group at 4:37 am on Wednesday, according to a statement by the group.

The group is a major state-owned coal mining company in Hebei, and the Qianjiaying subsidiary is located in Tangshan's Fengnan district, according to Xinhua News Agency.

After the cave-in, the two rescued individuals quickly hid under a tunneling machine. They were discovered around 7 pm on Wednesday.

Rescue workers manually excavated a rescue passage approximately 60 centimeters wide and high through the collapsed material.

According to the report by CMG, the collapse occurred at a working site more than 680 meters underground. As the workers were tunneling, the 10-meter-long tunneling machine encountered a fault. The upper rock layer collapsed, burying the machine and filling approximately five meters of the tunnel behind with rocks.

As of press time, rescue teams are intensifying efforts on site, equipped with professional equipment to comprehensively assess the underground situation and determine the exact locations of the remaining four trapped workers, the report said.