Most of the miners admitted to hospital had suffered carbon monoxide poisoning, Xinhua said, citing doctors at the Xishan Hospital of Coal and Electricity.

Shanxi Jiaomei is China's largest producer of coking coal and operates 28 mines.

The company said that the Gujiao unit was considered a relatively safe mine, with no accidents reported over the past decade.

Most lethal accident

While rescue efforts continue, the death toll of 73 already makes the Gujiao tragedy the most lethal accident reported in the country's mining industry since 105 people died in an explosion in December 2007, also in Shanxi.

China has vowed for years to improve safety at its mines, but has been hampered by a lack of resources to effectively supervise the industry, a major employer of destitute migrant workers.

Government figures show that almost 80 percent of the nation's 16,000 mines are illegal.

China attempted to reduce accidents by closing more than 1,000 small, dangerous mines last year, but the country's mining industry is still the world's deadliest.

According to state media, more than 3,000 people died in Chinese coal mines in 2008 alone.

Independent labour groups have long maintained that China's mining death toll is much higher than the government says.

Local mine bosses and regional leaders routinely cover up accidents to avoid fines and costly mine shutdowns, the groups say.