The bodies of 18 miners have been recovered as of Tuesday afternoon, after an explosion at a coal mine in southwest China's Chongqing Municipality Monday.
Fifteen miners remain missing and rescue work is still underway.
Altogether 35 workers were in the pit at the time of the accident, just after 11:30 a.m. Monday. Two escaped unharmed, leaving 33 trapped in a pit in Jinshangou Coal Mine, Yongchuan District.
Police are questioning the mine's management team, surnamed Jiang and Zhou, according to Luo Qingquan, head of the district government.
Preliminary investigations show the coal mine trespassed over its mining boundaries, had insufficient and malfunctioning equipment, poor ventilation and disorderly management, according to the rescue headquarters.
"I am greatly saddened that such a grave accident occurred. There are grave problems in the company with regards to ensuring safety, as well as loopholes in supervision," said Mu Huaping, vice mayor of Chongqing.
Mu said that there would be in-depth investigation into the cause of the accident to ascertain responsibility.
More than 400 rescuers worked through the night, digging carefully through debris to avoid secondary disasters, and at least 20 ambulances and dozens of medical workers are standing by.
Five teams of rescuers descended the shaft to search for missing miners and install ventilation equipment, Mu said.
Early on Tuesday, hazardous gas was expelled from the northern entrance of the shaft. Rescuers combed the area and found several bodies, he added.
Several sections of shaft collapsed after the blast, and rescuers had to bring planks to stabilize the internal structure of the shaft, he said.
At the time of the explosion, Tao Puzhang, 60, was working on his land about 500 meters from the mine when he heard a bang, and felt the ground shake under his feet. "The smoke from the blast shot up dozens of meters high. It was frightening," he said.
Liu Fuxiu, a winch operator at the mine, working 40 meters from the entrance to the pit, was knocked off her feet by the blast and received injuries to her face and back. "My injuries are nothing," she said responding to investigators. "I have a relative down the pit, and I hope he is still alive."
A 200-member work team is providing assistance to relatives of the miners.
Following the explosion, Chongqing has ordered a safety overhaul and temporarily closed all collieries with less than 90,000 tonnes of annual output.
The Jinshangou mine has a designed annual output of 60,000 tonnes, according to its license.
