Two persons, Prasanta Mahanta of Naoboisa and Anil Bora of Morigaon district, working with a health NGO were arrested on the basis of information provided by the deceased women's mother that the two had visited their house on the night of the murder, the sources said.
A post-mortem report of the two women stated that they were raped before being hacked to death, the sources said.
The bodies of the three victims without clothes and covered with only a blanket were recovered from their house at Haribordoloni Naoboisa, under Lakhimpur police station, after their neighbours informed police that they did not wake up the next morning.
The two women and the baby were alone at home with the men of the house away working as drivers in Arunachal Pradesh and the mother in another village, sources said.
The three bodies were cremated following their post-mortem, the sources added.