It said 13 miners were rescued and in hospital after the early morning explosion in the Rui Zhiyuan coal mine in Hongtong county near the city of Linfen in Shanxi province.
"Forty bodies have been found and 74 are still trapped," said a notice posted on the Web site of the State Administration for Work Safety.
The notice said the mine was properly licensed, was owned by the local government and had an annual output capacity of 210,000 tons of coal.
It said the mine's managers were being questioned by police and that the mine's bank account had been frozen.
The official Xinhua News Agency put the death toll at 46. There was no immediate explanation for the difference.
China's coal mining industry is the most dangerous in the world, averaging 13 deaths a day from fires, explosions and floods. In August, 181 miners died when heavy rains flooded two mines in eastern Shandong province.
Many of the accidents are blamed on mine owners who disregard safety rules and fail to invest in required ventilation, fire control and other equipment.
Meanwhile, 11 people were trapped after a roof collapsed in an iron- and gold-ore mine in Chengde in Hebei province, also in northern China, Xinhua said.
It said the accident in the private mine happened Monday but was not reported to officials until Thursday. It did not give the fate of the miners.
Xinhua reported separately that 12 people died of gas poisoning in the Xinjiang region in northwestern China.
It said the poisoning happened in an outdoor tent that was being used by workers digging for licorice root, a medicinal herb used in traditional Chinese medicine.