Police officials said the incident is of Domia village under Jokihat police station in the district and the deceased have been identified as Munni Khatun (35), her daughter Muskan (7) and son Dilshad (3).
Jokihat Station House Officer (SHO) M A Haideri said Munni's husband Mohammad Akhtaruddin is a migrant labourer, and she lived with children in her in-law's house.
"Yesterday around midnight she had a fight with her father-in-law Mohammad Jabul and mother-in-law Saeeda Khatun, after which she poisoned her children and consumed some herself," Haideri said.
Meanwhile, the parents of Munni have accused her in-laws of torturing and murdering her, and have registered an FIR against them.
The SHO said no bottle or packet of any poisonous substance has been found from the house where the incident happened. The bodies have been sent for postmortem and forensic examination.
