The deceased were identified as Pradeep Jaiswal (59), his son Rajan (34), daughter-in-law Anuja (33) and grandson Anshul (7), said a police officer.
There were six persons in the house when the fire broke out around 5.45 AM. All six were rushed to GTB Hospital, where doctors declared four dead on arrival.
Pradeep's wife Saroj and daughter Selja survived the blaze and were undergoing treatment at the hospital, he said.
The fire was suspected to have originated from a short-circuit in the family's dry-cleaning shop at the front side of their residence.
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Seven fire tenders were rushed to the spot and fire fighters took more than an hour to douse the flames, following which a cooling operation was launched.
Rajan, in his bid to save his family, locked his wife and seven-year-old son in the bathroom but they soon died of suffocation. After preliminary investigation, it emerged that Anuja and Anshul died of asphyxia and later their bodies caught fire, the officer said.
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Police have registered an unnamed FIR in connection with the incident.