Six members of a family - the parents, three daughters and a son - were found dead in a house here on Thursday, police said.
"Circumstantial evidence shows the family members committed suicide for reasons which have to be investigated," deputy commissioner of police Labhu Ram said.
The deceased were identified as Ganga Hanumaiah, 57, his wife Jayamma, 54, their three daughters - Hemalatha, 30, Vimala, 28, and Nethravati, 24 - and son Yatish, 26.
Hanumaiah was working with the state-run Bharat Sanchar Nigam Ltd. (BSNL), while his wife was a homemaker.
The eldest daughter Hemalatha was working in an IT firm and the second daughter Vimala with the railways. The youngest daughter was an engineering student and the son was unemployed.
"Hanumaiah's body was found hanging from the ceiling while the bodies of his wife (a paralytic patient) and children were on cots in a sleeping position, which indicates they could have consumed poisoned food," the police official said.
Police registered a case of unnatural death.
"We suspect Hanumaiah hanged himself after feeding poisoned food to his wife and four children, as is evident from the scene at his house," Ram added.
The shocking incident came to light when one of the tenants living in the same building saw through a window Hanumaiah's body hanging and alerted the police.
The bodies were taken to the state-run Victoria Hospital for autopsy.