Rising water levels in the mine near Baotou city in the Inner Mongolia autonomous region prompted officials to abandon rescue efforts on Tuesday, state news agency Xinhua reported.
Work at all mines operating in the area has been suspended until "they were proved legal and safe after a thorough examination", Xinhua said.
The cause of the flooding in the Haolaigou mine which occurred early on Wednesday has yet to be ascertained.
Güncelleme Tarihi: 20 Eylül 2018, 18:16
Thirty-five miners were originally trapped when the mine flooded, but six managed to escape after a day underground.
The six men were recuperating in a nearby hospital, city officials said.
No contact had been made with the trapped men since the flooding.
"Experts believe the survival chances of the miners are slim as the water level in the shaft would be well above their heads," Xinhua reported.
It said recuers estimated the shaft had only enough oxygen for one man to survive two days.
China's mines are the most hazardous in the world and every year thousands of Chinese miners die in flooding, gas explosions, fires or are buried alive.
Labour rights groups say safety standards are routinely compromised in the haste to extract resources required by the country's energy- and resource-hungry industries.