Rescuers have recovered the bodies of all seven miners killed in a colliery explosion in southwest China's Chongqing Municipality, local authorities said Friday.

The accident occurred at about 5 p.m. Thursday when the seven miners were working at Jiuli Coal Mine in Fengjie County.

An investigation found the explosion was caused when blasting ignited gas that had accumulated in the mineshaft due to a malfunction of the mine's ventilation equipment, said a statement from the publicity department of the county committee of the Communist Party of China.

After pumping air into the shaft all night, rescuers were able to enter the pit at daybreak and found four bodies in the shaft. The other three were found early Friday.

The mine, with an annual output of 20,000 tons, is privately-owned. Its owner has been detained by police pending a complete investigation.