The recruits were staying in two buildings at the Fuzhou Command School of Armed Police in Fujian province when torrential rain triggered by Typhoon Longwang sent torrents of mud crashing down a hillside, sweeping them away.
President Hu Jintao ordered an all-out effort to find them after the incident on Sunday night, and military and police teams were coordinating operations, the Xinhua news agency said.
With rumours swirling that the toll could be higher, local media at the scene said they had been instructed not to report the incident, with details only being released through state-controlled Xinhua on Tuesday.
The school refused to comment.
"We haven't received any instructions to release information on our relief work," said a staff member in the academy's head office.
Longwang landed in Fujian on Sunday night after leaving at least one dead in Taiwan. So far, three people are confirmed dead on the mainland.
The storm, which has weakened to a tropical depression, forced the evacuation of nearly 600,000 people in the provinces of Fujian and Guangdong, with 5400 houses destroyed and vast tracts of farmland ruined.
Economic damage was estimated at $150 million, the China Daily reported, with the tourism sector bearing the brunt on what would normally have been one of the busiest times of the year, during the National Day holiday.
Almost 600,000 were forced to
evacuate two provinces
In the Fujian capital, Fuzhou, water rose to two metres in some areas after a nearby river flooded, paralysing the city's transport system.
Serious flooding was also reported in central and northern China, with at least three people killed in Shaanxi province, which has been pounded by heavy rain for a week.
Two of the dead were students swept away by flood waters in Xixiang county.
Nearly 1000 houses have been toppled and about 17,000 people forced from their homes, said Tan Cewu, director of the Shaanxi Provincial Water Conservation Department.
"The flood is still under control, though it seems still severe"
Deputy director of the flood control headquarters of the Yangtze River
In the central province of Hubei, 13,000 residents fled rising waters along the banks of a tributary of the Yangtze River in Wuhan city, Xinhua reported.
Heavy rain has been pounding the Danjiangkou Reservoir along the upper reaches of the Hanjiang River since Thursday, flooding some counties and cutting off several roads in the area.
"The flood is still under control, though it seems still severe," said Cai Qihua, deputy director of the flood control headquarters of the Yangtze River.
More heavy rain is forecast in the days ahead.
Floods have always been part of life in China, although officials have said this year has been more devastating than usual.
Official figures released at the end of August showed floods had killed 1024 people, and left another 293 missing in China this year. More than 150 million people have been affected.
Typhoon Longwang made landfall
on Sunday in Fujian province
Since serious flooding of the Yangtze River in 1998, China has spent billions of dollars on flood mitigation.
Major rivers have been brought under greater control, and early warning systems have been put in place, but flash floods and landslides caused by unprecedented rains continue to cause major damage.