HEGANG: Hopes of finding more survivors from a huge coal mine blast in China took a blow Monday with the recovery of 12 bodies, raising the death toll to 104 in the nation's worst mining disaster in two years.

Rescuers were braving mine shafts full of toxic gas in a desperate search for four workers still missing in the mine in Hegang city in northeast China, as grieving relatives of the victims angrily demanded answers.

"Rescue operations are still continuing. If we haven't found them yet we believe they are still alive," mine spokesman Zeng Jinguang told reporters, confirming the latest death toll.

"If there is any chance of finding them we will not give up."

The explosion tore through the state-run mine in Heilongjiang province near the Russian border early Saturday after a build-up of gas, the latest tragedy in the country's notoriously dangerous mining industry.

Smoke could still be seen on Monday billowing out of an entrance to the mine, one of the largest and oldest in China, as authorities turned to the task of dealing with the relatives.

Zeng said psychologists were being brought in to help survivors and relatives of victims cope with the disaster.

A group of women waited outside an entrance to the mine office in sub-zero temperatures, crying and shouting in despair.

"I haven't had any news. My husband was only 42," wailed one of the women, tears streaming down her face.

A second woman also complained that her family had received no information about the fate of her younger brother, who was in the mine at the time of the accident.

"It was my little brother. It's been three days and still we haven't had any news," she cried.

The women, who would not provide their names to AFP, were later escorted into the mine office.

The accident was the worst in energy-hungry China since an explosion killed 105 miners in Shanxi province in December 2007. Chronology: Major accidents in Chinese mines

A total of 528 miners were in the pit when the blast occurred, according to the State Administration of Work Safety, and local news reports said it was so powerful it was felt 10 kilometres (six miles) away.

Mine spokesman Zeng said none of the more than 60 people who were hospitalised after the explosion were in life-threatening condition.

Chinese media reports have quoted survivors saying they were frantically trying to flee the mine amid a gas build-up when the explosion occurred.

On Saturday, President Hu Jintao and Prime Minister Wen Jiabao issued orders to take all measures to rescue workers at Hegang.

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 reported.

State media reports also have said an investigation would be launched into whether negligence played a part in the disaster.

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.

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 to avoid costly mine shutdowns.