The deceased persons were identified as Shakuntaka Sahu (60), her married daughter Rosalin (36), sons Asish (34) and Jyotiranjan (30). They were family members of retired forest department personnel Arjun Sahu, police said.
Police said Arjun Sahu took the four to Dhenkanal District Headquarter Hospital where doctors declared them brought dead.
Dhenkanal Sadar Police Station inspector-in-charge Pradip Pradhan said the police was suspecting it could be a case of suicide. Preliminary investigation indicated the four persons might have consumed excess doses of chloroquine tablets, he said.
The bodies were sent for post-mortem and further investigation was on, police said.