The death toll from a coal mine blast in northeast China climbed to 92 on Sunday as rescuers hunted for 16 workers still trapped deep underground in the nation's deadliest mine disaster in two years.

The explosion early Saturday tore through the state-run mine in Heilongjiang province, near the Russian border, after a build-up of gas, survivors said.

With the main entrance blocked by debris, rescue teams equipped with oxygen tanks were accessing the shaft from an adjacent mine, braving high gas levels to search for survivors, an AFP reporter witnessed.

The death toll jumped to 87 early Sunday and had reached 92 by late evening, state news agency Xinhua said, quoting unnamed authorities in Hegang city, where the mine is located.

Efforts to rescue the 16 believed trapped continued late into the evening. Two AFP reporters were escorted by officials to the blocked entrance, where over 30 rescuers prepared to enter the adjacent mine in freezing weather.

Clouds of smoke -- remnants of the explosion -- billowed out of the blocked entrance.

"We were preparing to evacuate when the explosion occurred, sending glass and rocks flying everywhere," miner Wang Xingang told China National Radio.

"We began running out and shouting to evacuate. Smoke was everywhere. I couldn't see at all. I was trying to feel my way out from my memory of the shaft."

The explosion occurred with 528 miners in the pit, according to a statement by the State Administration of Work Safety.

Local news reports said the blast was felt 10 kilometres (six miles) away and has also left more than 60 miners in hospital.

"Most of the injured are suffering from compound injuries, like respiratory injuries, broken bones and gas poisoning," Pan Xiaowen, director of Hegang general hospital, told radio.

The accident was the deadliest of its kind in the energy-hungry nation since an explosion killed 105 miners in Shanxi province in December 2007.

"I was with a group of 10 miners.... Right now I don't know if they made it out," mining veteran Fu Maofeng, 48, told the East Asia Trade News from his hospital bed.

Miners near the shaft entrance were told to evacuate after gas levels in the mine rose sharply, he told the paper. When he and two others reached the entrance, a huge blast ripped through the main shaft, he said.

Rescue workers have identified 28 areas in the mine, some 500 metres (1,650 feet) below ground, where teams were working at the time of the blast.

One miner, identified as Hu Yu, told the China Youth Daily he had nearly passed out due to gas in the mine two hours before the explosion and was almost delirious as he fled the shaft.

On Saturday, President Hu Jintao and Prime Minister Wen Jiabao issued orders to take all measures to rescue workers, while Vice Premier Zhang Dejiang was dispatched to the mine to oversee the operation, state media said.

The head, deputy head and chief engineer of the mine, which is run by the majority state-owned Heilongjiang Longmay Mining Holding Group, have been removed from their posts, the China News Service said.

China's state prosecutor will launch a probe to determine whether criminal negligence led to the disaster, China Central Television said.

On Sunday, the provincial work safety bureau vowed to step up a reform of the industry and shut down small inefficient mines in the region, Xinhua said.

China's coal mines are among the most dangerous in the world, with safety standards often ignored in the quest for profits and the drive to meet surging demand for coal -- the source of about 70 percent of China's energy.

The central government has campaigned in recent years to modernise its collieries and control the leakage of gas, particularly methane, which is often responsible for mine explosions.

Official figures show that more than 3,200 workers died in collieries last year, but independent labour groups say the actual figure could be much higher, as accidents are often covered up in order to avoid costly mine shutdowns.

Separately Sunday, in central Hunan province, six workers were killed in an accident at a private mine, Xinhua said quoting local authorities.