Efforts to pump water out of the coal mine did not begin until five days after the May 18 flood, reportedly because of technical problems and lack of power to run the giant pumps brought in by rescuers.
But Li Yizhong, director of the State Administration of Work Safety, said Wednesday, "We will try our best to save them even if there is only the slimmest chance they are alive," the official Xinhua News Agency reported.
The new 30-centimeter wide (foot wide) hole would give rescuers another way to access the flooded shaft, the report said.
Li has blamed a deadly mix of poor management and lax oversight by local officials for the accident, the AP reports.
So far 19 people, including the mine's owner, labor contractors, bank officials and workers in charge of detecting water have been detained by police, according to Xinhua.
China's coal mines are the world's deadliest, with about 6,000 deaths every year in fires, floods and explosions, often blamed on indifference to safety rules and lack of required equipment.