Rescuers carry the body of a victim at the Xiaojiawan Coal Mine in Panzhihua, Sichuan province An explosion killed 43 miners. (China Daily/Reuters)

An initial investigation into China's worst mine accident in nearly three years blames "chaotic" management for sending too many workers underground and disregarding safety measures, state media said Sunday. The blast killed 43 people.

The official Xinhua News Agency said that though the Xiaojiawan coal mine in southwestern Sichuan province was licensed to operate, it had been exceeding its production capacity in violation of safety standards.

Rescuers were still searching for three miners who remained trapped underground after the explosion on Wednesday afternoon in the coal-rich city of Panzhihua, but their chances of survival were slim. State media said the three workers were believed to be located at the centre of the blast.

A preliminary probe found that the accident happened because production had not been stopped despite a high density of gas and that safety monitoring equipment was inadequate, Xinhua said.

More miners had been sent to work underground than were allowed to, the report cited the head of the State Administration of Work Safety, Yang Dongliang, as saying.

Police have detained the mine owners, and the Sichuan government has launched a province-wide safety check on all coal mines and pledged to shut down those with safety hazards.

There were 154 miners working at the mine when the explosion occurred, and 108 survivors have been pulled to the surface.

It is China's deadliest mine accident since November 2009 when 108 people were killed in an explosion in a mine in Heilongjiang province.

Xinhua said the rescue work was dangerous because of high temperatures in the mine and dense carbon monoxide that meant only mask-wearing paramedics were able to enter the shaft.

The news agency quoted one miner, Xu Changyong, as saying he heard the explosion and then ash started coming out of his air compressor before he scrambled out of the mine.

Of the miners who made it to the surface, 50 are suffering from carbon monoxide poisoning and seven are in critical condition, Xinhua said.

The mine is owned by Zhengjin Industry and Trade Co. Ltd. and the owners were in police custody for investigation, the Panzhihua city government said.

Coal mine accidents are common in China, where work safety rules are often ignored. Last year, 1,973 miners were killed in coal mine accidents in the country, but that was down 19 per cent from the previous year as authorities continue to beef up safety measures.

The State Administration of Work Safety said recently that it planned to close more than 600 small coal mines — considered more dangerous than larger mines — this year to further reduce fatalities.