The incident was reported from Rajendra Park Extension. A neighbour found six persons lying unconscious inside the house this morning and informed the police.
Police rushed them to Deen Dayal Upadhaya hospital where Prempal (40), Akhilesh (17) and Vikas (4) were declared brought dead.
Devkali (35), Lakshmi (10) and Amit (7) were undergoing treatment in the hospital.
A senior police official said they were investigating the cause of death. "It may be a case of suffocation. Food poisoning could be another reason," the official said.
Bodies have been sent for postmortem.