Rescuers racing to save 19 trapped coal miners in south China suspended their efforts Monday morning due to high levels of toxic gas.

After carbon monoxide gushed out of the mine at 2:45 a.m., the rescue command center ordered the rescuers to retreat to the platform of the main shaft, said Ye Fangyong, an expert from the command center.

Ye added that other toxic gas in the mine is also over the safety level.

As of 9:30 a.m., the command center was still trying to identify the source of the carbon monoxide and find a solution to recommence the rescue operation. Ye said the rescue will resume as soon as possible.

The collapse occurred midday Saturday in the suburbs of Heshan City in Guangxi Zhuang Autonomous Region. Initial investigations indicate that the collapse was caused by continuous heavy rains.

Forty-nine of 71 miners managed to escape when the coal mine collapsed, and rescuers have retrieved three bodies of the dead miners.

The location of the trapped miners has been identified, but their conditions are unclear, according to the rescuers.