The incident took place last evening under Padbanabham mandal when they entered the tank for swimming and were suddenly caught in the heavy currents.
The deceased were identified as K Kalyan (14, his brother K Mohan (12), S Vinay (14) and J Simhachalam (14),Inspector S Kanta Rao said.
Locals spotted a cricket bat and clothes lying at the spot around 7.30 PM yesterday and alerted police following which the bodies were fished out and taken to government K G hospital for postmortem.