"There is little chance that the people who are trapped will be able to survive," Xue, an official in Guizhou, said.
Hui Liangyu, the Chinese vice-premier, arrived at the scene on Monday night to oversee rescue efforts, the official Xinhua news agency said.
Large areas of southern China have been hit by flooding in the last two weeks, with at least 377 people killed and another 142 missing, excluding Monday's landslide.
China's civil affairs ministry said more than three million people have had to flee their homes over the past two weeks.
On Sunday, floodwaters began receding in the hard-hit south, and workers finished repairing a dyke breach that forced the evacuation of 100,000 people.
But torrential rains have continued in the region where Monday's landslide occurred.