A 24-year-old man was arrested on May 25 in murder of nine people in Telangana's Warangal district in India last week.
The bodies of six from a family and three others - two from Bihar and one from Tripura- were found in a well in a village about 150km from state's capital Hyderabad, reports NDTV.
The accused Sanjay Kumar Yadav killed them to cover up the murder of a woman who went missing in March, police said.
The accused killed all nine of them after spiking their food with sleeping pills and then throwing them in a well.
The murders in Geesugonda Mandal village were carried out to cover up the killing of a woman, related to the family, by the accused, Warangal Police Commissioner V Ravinder told reporters.
"To cover up one murder, he killed nine others," the official said, adding that police would ensure maximum punishment for the accused.
Sanjay had allegedly murdered a woman on March 6.
Six of a family - Maqsood, his wife, their two sons, daughter Bushra and her 3-year-old son - were found dead last week. along with three others. Officials said seven of those found dead were working at a gunny bag-stitching unit.
Maqsood was a 48-year-old man who migrated from West Bengal over 20 years ago and had settled down in Warangal Rural. His family had been staying in two rooms on the premises of the unit, police sources said.
Maqsood's wife had reportedly threatened Sanjay Yadav, who is from Bihar, about reporting the missing woman to the police. So he hatched the conspiracy, said officials concerned.
When the bodies were found initially, a possibility of mass suicide was not ruled out as no major injury marks were found. Later, scratch marks on the bodies led the six special teams to the alleged killer who is said to have confessed to the murders.