A country boat, carrying six persons, was on its way from Patepadar to Kanasakuli under Thuamul-Rampur police station limits when it capsized after the boatman lost control, said Kalahandi District Additional Superintendent of Police (ASP) Dinajan Nayak.
While two persons managed to swim ashore, there was no trace of the four others, the ASP said.
"We have launched a search operation to trace the remaining four persons in the reservoir," the ASP said, adding, rescue operation is going on.