The sound was heard around 2 a.m. Monday in response to rescuers' knocking at a 270-plus meter deep hole that had been drilled Sunday night, rescuers said.
The hole can supply ventilation to the area where the miners might be trapped, and it can be used to send water and food, China Daily reported.
The flooded mine in Heilongjiang province belongs to the Hengtai Coal Mining Co. The flooding occurred last Tuesday when the miners were working underground.
Nineteen other miners managed to escape. Three others were rescued Saturday while a body of another miner was retrieved Sunday.
The provincial government ordered the mine to stop production in 2007, but its owner resumed production without permission, the work safety bureau said.
The accident happened when workers mistakenly drilled into a neighbouring mine, the newspaper said.
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