Seventy-one miners were in the shaft when the blast occurred on Thursday afternoon at Nanlou township near the city of Yangquan in the northern province of Shanxi, a county official told reporters on Friday.
Twenty-eight miners died in the initial explosion and five others perished during a rescue attempt, he said. Everyone else escaped.
Of the survivors, 24 were hospitalised, 18 of them suffering from carbon monoxide poisoning, doctors at the Yu county hospital told Xinhua news agency. None of the injured is in danger of dying.
The accident comes less than two weeks after 166 people were killed in a coal mine blast in neighbouring Shaanxi province in the country's worst mining disaster in 44 years.
A gas explosion in October killed 148 miners in the central province of Henan. "It is a problem of mine management and a lack of safety awareness," An Yuanjie, information director for the State Administration of Coal Mine Safety, told reporters.
"Overproduction exceeding mine capacity, especially in the
More than 7000 workers are killed
each year in China's coal mines
small mines where there is already a lack of safety facilities, as well as inadequate investment in safety infrastructure - these are all the reasons that are causing these coal mine disasters," she said.
"As the national administration of work safety we need to strengthen our efforts to supervise these mines."
Experts blame most accidents not just on poor safety but the
government's failure to enforce regulations. While the government said it closed down 60,000 small mines in the last decade because they were considered unsafe and inefficient, soaring demand has led to many being reopened.
As well as safety concerns, China's miners have to deal with
health issues. According to recent state media reports, about 600,000 miners suffer from pneumoconiosis, a disease of the lungs caused by inhalation of dust. The figure is increasing by some 70,000 miners every year, Xinhua said.
China depends on coal for 70% of its energy and has significantly increased production in the past year to meet the demands of rapid industrialisation.
Critics and miners say lives are being sacrificed in the quest
for energy. More than 7000 workers are killed each year in China's coal mines, considered the world's most dangerous.