Rescuers poured milk down a coal mine's ventilation pipes in a bid to save 69 workers trapped underground for more than 50 hours in central China, state media said Tuesday.

The Xinhua News Agency said authorities were maintaining contact with the workers via a fixed line telephone, and there were no reported injuries.

The 69 were trapped when the state-owned Zhijian mine in Henan province's Shan County was flooded early Sunday. Thirty-three miners managed to escape.

Late Monday, 400 kilograms of milk was sent down 2,624-foot long ventilation pipes into the pit, it said. Rescuers were hoping the milk would "prolong the miners' lives and give rescuers more time to eventually save them," it said.

Xinhua said earlier that the area where the miners were trapped was dry and had electricity but that ventilation was poor. It said oxygen was also being piped into the pit.

Hundreds of rescuers were struggling to prevent more river water from entering the mine, pumping out water from the shafts and clearing away silt, it said.

China's coal mines are the world's deadliest, with fatalities reported nearly every day in fires, explosions and floods despite government efforts to improve safety.

Deadly accidents often are blamed on mine owners who disregard safety rules and fail to invest in required ventilation, fire control and other equipment.