A couple and their daughter were found murdered at their house in Assam's Jorhat district on Saturday, the police said.
The police said they suspect the mother and her daughter were raped before they were killed on Friday night.
A suspect has been identified and police teams are looking for him, an officer said.
The bodies were found by their neighbours on Saturday morning, the police said.
The man, a resident of Sonitpur district, was the caretaker of a brick kiln near the house. A shirt and a knife were recovered near the house, the police officer said, adding they are further investigating the crime.