No one knows exactly how many miners were inside when the Daxing Coal Mine in Xingning city, 265km northeast of Guangzhou, flooded on Sunday afternoon.
The managers in charge had all fled, government officials said.
Officials on Monday said 101 miners were trapped, but state media on Tuesday said there were at least 102. More people were coming forward, however, to report missing relatives.
"The number of trapped miners is probably higher than 102, which we estimated yesterday," An Yuanjie, a spokesman for the State Administration of Coal Mine Safety in Beijing, said.
"We need time to check the exact number because this coal mine is privately run, the management is not good. Secondly, all the managers ran away after the accident. So, it's hard to get the correct number at the moment."
There are usually more than 200 miners working in the pit, the China Daily quoted a local resident as saying.
More than 200 miners usually
work in the pit, a witness said
"Almost all the miners were working when the accident happened," the man surnamed Wang was quoted as saying.
Water accumulated underground had reached between 15 million to 20 million cubic metres, making rescue work "very difficult", An said.
"In fact, the entire coal mine is full of water. Hope for the miners is slim, but the rescue work is still continuing," An said. State media reported the shaft could hold as much water as a medium-size reservoir.
More than 600 rescuers were trying to save the miners but their progress was severely hampered by the depth of the water, a local official said.
The trapped miners were 480 metres underground when the accident happened. Only four escaped.
Photos from the scene showed muddied rescuers working intensely to try to install high-power pumps to clear away the flood waters.
China's mines are considered the
It was difficult to pump out all the water because water was still gushing into the shaft and experts could not locate its source, officials said.
Local authorities issued a notice on Monday calling for the 65 managers who fled to return and help with the investigation.
The accident highlighted the deadly consequences of China's drive to extract more coal to power its rapidly growing economy.
China relies on coal for 70% of its energy needs.
It also shows the lack of enforcement of safety rules and mine closure orders, as mine owners put profits ahead of lives.
The privately-owned mine, along with other mines in the area, had been ordered to shut after another mine flood in the same town last month, but the owners ignored the orders, the official Xinhua news agency said.
The company did not have a licence to mine. The cause of the flooding was under investigation.
Officials have ordered all mines in the county to suspend operations pending safety inspections.
China's mines are considered the world's deadliest.