A cowherd called Nagabhusanam spotted the bodies and alerted the Duttalur police.
The deceased were identified as Venkateswarlu (60), his daughter Padma (33), her daughter Sravana Sandhya (15) and son Shiva (12), all residents of Narravada village.
Atmakur DSP Subba Reddy said that they seemed to have committed suicide by drinking pesticide about a week ago, due to some family problem. Further probe is on.