The incident occurred at Kushfara village, around 20 kilometres from the district headquarters, they said.
Rescue operations have been initiated and divers have been pressed into service to look for them, Mandhata police station in-charge MP Singh said.
"Raunak Singh (17), Shivaang Singh (16) and Avneet Upadhyay (17) were taking bath in the river this afternoon, when they were swept away by the fast currents, he said.
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