Sources said that when Usman, who lives with the family, arrived back home after work and repeatedly knocked at the main door but to no avail.
Consequently, the neighbours informed the local police who arrived at the scene and knocked down the door to find the three bodies.
The bodies have been shifted to hospital for postmortem.
Boy 'killed' by brother-in-law
The mother has been identified as Ayesha and her two daughters: Ayyan, 2, and Noor, an 8-month-old.
According to police, there were no injuries found on any of the bodies and they believe that their deaths were caused by consuming a toxic substance.
However, the cause of death shall only be ascertained after the postmortem reports come to fray.
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