HARBIN, June 12 (Xinhuanet) -- The body of one more primary school student was discovered late on Sunday, bringing the death toll in the flash flood in northeast China's Heilongjiang Province to 92 by 6 p.m., local rescue headquarters said.     Earlier repoart said that death toll rose to 91 in Heilongjiang as of Sunday morning and 25 others are hospitalized.      The victims included 88 primary school students and four villagers in Shalan Town of Ning'an City, which was hit by a heavy flood and ensuing mountain torrent Friday afternoon.     Another 17 students remained missing, and rescue operation is continuing tensely, said an official at the rescue headquarters.     Seven out of 18 villages in Ning'an City have been damaged by the floods. About 1,333 hectares of farm land were devastated, 55 houses collapsed and 1,800 villagers' life were affected in the catastrophe.     The rescue team is clearing the flood-hit primary school and searching efforts have been reinforced in an expanded area along the flooding river ways.     The complicated conditions in the watercourses have hampered the rescue work, but rescuers are continuing their search for the missing, according to Zhao He, head of a team of rescue soldiers at the site.     Provincial Governor Zhang Zuoji and other high-ranking officials with the provincial government are guiding rescue work on the spot.