The accused who was currently living in a rented accommodation here on Tajpur road, had kidnapped the minor from the labour quarter.
The committee headed by NCW chairperson Rekha Sharma would travel to Bihar later this week to meet the survivor.
The men allegedly raped one of the girls while the other managed to escape and rushed to her home, police said.
A police official said Sunday they are investigating the case from various angles, including an old enmity, if any, between the girl's father and his friend.
It was found that the woman had poisoned the boys as a punishment for allegedly stealing food from her house.
The boy was arrested on Tuesday and sent to a probation home in the neighbouring Hazaibag district, the OC said.
5-year-old Kendriya Vidhyalaya student raped in Raipur, principal arrested for not reporting incident
The minor was allegedly raped by three 10-year-old boys of Class-5 in the school’s bathroom previous week.
When the accused saw them plucking leaves, he got enraged and blocked the victim's way by driving his car back and forth.
He said a detailed monitoring mechanism should be put in place to ensure investigation and trial in sexual offences/ rape against girls below 12 years of age are completed within two months.
The body has been sent for postmortem and further investigation is underway.
The girl's torso, kept in a plastic bag, was recovered from a bush around 4 kilometre from Tatanagar railway station, where she was kidnapped.
The incident came to light when the girl, along with her mother, visited the Kavali Hospital for abortion on July 27.
The trio, in their 20s, gangraped the 13-year-old while she was about to respond to nature’s call at an open place, after taking her to a remote place.
An FIR was lodged by the girl’s family against four people on Saturday under all the relevant sections.
The accused abducted the girl, took her to an abandoned house and raped her.