HEGANG, China, Nov 24, 2009 (AFP) - Too many miners were below ground at a Chinese coal mine where 104 workers were killed in a gas explosion, a safety official charged, as rescuers pressed on Tuesday with the hunt for four missing men.

Press reports quoted Zhao Tiechui, deputy head of the state work safety agency, as saying overcrowded shafts were among the factors in the disaster at the Xingxing mine in northeastern China, the deadliest such blast in two years.

"Excessively large coal faces being mined, too many people below ground and insufficient ventilation were factors in the accident," Zhao was quoted saying by various media.

The explosion tore through the mine in the frigid rust belt city of Hegang in Heilongjiang province early Saturday when more than 500 miners were below ground, officials said.

A total of 104 people have been confirmed dead and a mine spokesman said rescuers working in sub-zero conditions are still trying to reach the missing four, who are believed to have been close to the centre of the blast. "The rescue work is ongoing. As long as there is hope, we will continue our efforts," spokesman Zhang Jinguang told AFP.

Relatives of the victims have angrily demanded answers about the disaster as officials said a preliminary investigation pointed to poor management at the mine, one of China's oldest and largest.

There was a heavy police presence at the mine, apparently aimed at preventing protests, but the area was quiet on Tuesday.

The state-run Global Times newspaper reported that safety authorities had recently granted the mine a clean bill of health on safety.

The head, deputy head and chief engineer of the mine have been removed from their posts, state press reports have said.

Qi Weiping, an official with the majority state-owned Heilongjiang Longmay Mining Holding Group which owns the mine, also hinted at shortcomings during a briefing to reporters.

"As China is currently modernising and industrialising, the situation in some areas is not yet up to the overall level of development," Qi said. He declined further comment, citing the ongoing investigation.

The accident was the worst in energy-hungry China since an explosion killed 105 miners in Shanxi province in December 2007, and has reignited concern over safety and working conditions in the country?s mining sector.

Authorities have announced compensation of up to 300,000 yuan (S$608,704) for relatives of dead miners as they moved to try to quell public anger.

Psychologists also were being brought in to help survivors and relatives of victims cope with the disaster, which also injured more than 60 people.

An injured miner who gave only his surname Wang hinted at the emotional damage as he recuperating at a hospital in Hegang.

He was preparing to go down the mine when the explosion occurred, and the blast of air from the explosion hit him in the face, leaving his now-bandaged face with cuts and burns.

"We all got along well every day," he said of colleagues who did not make it out alive. "My heart is really heavy. They never made it back up."