The death toll in a massive coal mine explosion in central China rose Wednesday to 166 after scores of missing miners were declared dead, government radio reported.

The report on the Web site of China National Radio came after officials said rescue efforts were being blocked by fires and toxic fumes in the Chenjiashan Coal Mine (search), which was hit by the huge gas explosion on Sunday.

The death toll earlier was reported at 65, with 101 miners still missing. The one-sentence report by China National Radio, which cited a spokesman for the rescue headquarters, didn't say whether any additional bodies had been found or give any other details.

The accident was the deadliest to hit China's accident-plagued coal mining industry in at least five years and occurred despite a government safety campaign to reduce fatalities among miners.

In a separate accident, a government news agency reported that 13 people were killed and three missing in an explosion early Wednesday in a coal mine in the southern province of Guizhou (search).

The blast Sunday in the Chenjiashan mine occurred some five miles from the mouth of the vast mine.

Emergency workers descended into the mine on Monday to repair ventilation equipment needed to clear away toxic carbon monoxide fumes from the explosion. But as late as Tuesday evening, state media said some areas were still too dangerous to enter.

An expert quoted Wednesday by the official Xinhua News Agency said the explosion would have blasted miners with temperatures up to 2,400.

"The carbon monoxide density there was so high that one breath was fatal," the expert, Zhou Qingyun, was quoted as saying.

The disaster Sunday came just weeks after another coal mine explosion killed 148 people elsewhere in central China — the highest death toll in a mining accident since 2000.

The Chenjiashan mine employs 3,400 people and produced 2.3 million tons of coal last year, according to Xinhua. It said another gas explosion there in 2001 killed 38 people.

China's coal mines (search) are the world's deadliest, with 4,153 people reported killed in the first nine months of this year in fires, floods and other disasters. The government says China accounted for 80 percent of all coal mining-related deaths worldwide last year.

Fires and explosions often are blamed on disregard of safety rules or lack of required equipment needed to remove natural that seeps from the coal bed.

The government has promised repeatedly to reduce the carnage in coal mines. But officials say severe nationwide power shortages might be increasing pressure for mines to raise coal production, boosting the risk of accidents.