County search and rescue units comb the Jordan River near 650 North and 15th West Thrusday morning after schoolchildren said they saw a boy jump in the river about 8 a.m. A medical helicopter also joined the search, flying over the banks of the river. Several students at Backman Elementary School reported the incident to their principal. Attendance records at Backman, which is adjacent to the river, were checked and all of the students accounted for. Officers ended a brief but intesive search early in the afternoon and did not continue into the night. Dispatchers said Friday morning that no missing person reports had been filed later in the day or during the night. Police would not elaborate Friday on theories that someone jumped in the river to play a prank on the 7-and 8-year-old schoolchildren, or that the children saw someone by the river but mistakenly thought he had jumped in.