PANZHIHUA, Sichuan -- The death toll from a gas blast that occurred Wednesday afternoon in a coal mine in southwest China's Sichuan Province has climbed to 26, rescuers said Thursday.

As of 8:40 pm, 21 miners remained trapped underground, and their conditions were not immediately known, sources with the rescue headquarters said.

Rescue efforts at the Xiaojiawan Coal Mine in the city of Panzhihua were proceeding but were hampered by high temperatures in the gas-filled pit, according to the headquarters.

Temperatures reached 80 to 90 degrees centigrade and carbon monoxide was dense in the zone where the miners were trapped. Currently, only some mask-wearing ambulancemen have been able to enter, authorities said.

A total of 154 miners were working underground when the accident happened at around 6 p.m. Wednesday, and 107 of them were rescued out of the shaft. Fifty-one miners were sent to hospitals, among them seven were critically injured.

The coal mine, some 750 km southwest of the provincial capital Chengdu, is owned by Zhengjin Industry and Trade Co, Ltd.

The owner of the mine is under police custody.