The spokesman for the mine declared all the 166 miners were killed, confirming what authorities had been expecting in the days since Sunday's accident.

More than 120 workers escaped Chenjiashan coal mine after the explosion, or what may have been back-to-back explosions. Many were seriously injured.

High temperatures and a buildup of toxic gas had slowed the search for bodies at the mine where until Wednesday 65 workers had been known to have been killed, with 101 trapped and presumed dead.

"In an environment with a high density of coal, gas and carbon monoxide, it's impossible that the miners still trapped underground can survive," Huo Shichang, head of the provincial coal mine industry administration, told a news conference earlier on Wednesday.

Sunday's blast was the worst since a September 2000 explosion in southwestern Guizhou province killed 162 people.