Mine operators "ignored safety rules and ignored the law", state broadcaster CCTV said, adding that when the blast occurred they delayed reporting the accident to authorities, waiting more than five hours before raising the alert and calling for outside help.
In that time the mine operators tried to mount their own rescue operation, but the improvised rescue crew was untrained and poorly equipped and at least 15 died after being overcome by carbon monoxide fumes, state media said.
Reports said another 15 miners had escaped with minor injuries, but the exact number of miners underground at the time of the blast was unclear.
The State Administration of Coal Mine Safety said on Sunday that the search for survivors had been called off.
China's coal mines average 13 deaths a day from fires, explosions and floods, making them the world's deadliest.
Chinese mine owners are regularly criticised for attempting to hide accidents from the authorities to avoid being fined or shut down.
Many mine operators cut corners in pursuit of production bonuses, egged on by the booming economy's voracious appetite for coal to generate electricity.
In a rare bit of good news on Monday, reports said 11 men had been rescued from a collapsed iron and gold mine north of Beijing after being trapped underground for more than five days.
The rescued miners said they ate paper and chewed on a boiled leather belt to stay alive, local media said.
"At first, we ate newspaper pages when we got hungry, then orange peel," Wu Pengyong, a 33-year-old miner, was quoted as saying.
"Later we got really hungry. I had a leather belt. I boiled it but it wouldn't cook. I divided this half-cooked belt out with everyone to eat."
Xinhua said the miners were in stable condition and were able to walk out with the help of rescuers.