However, the three youths were booked a year ago after the incident under Sections 363, 366, 376 and 506, at Makhi police station on June 20, 2017.
A special court in Lucknow sent Sengar, the prime accused in the case, to seven-day CBI custody, they said.
Earlier a report had claimed that the victim was around 19 years when she was raped last year.
Sources here on Monday said that CBI was reported to had taken a decision of narco test after it found discrepancies in the statements of the MLA during interrogation.
"The MLA was given a similar set of questions after a gap of one hour by interrogating officers".
"Later a custom broker, Himanshu Ajmera, came to meet the Customs official claiming to be a representative of Avista Multi Trade and allegedly offered him a bribe", he said. The CBI teams is likely to take the BJP MLA and Shashi Singh to the spot during recreation of crime scene.More news: Twitter Users Hilariously Slam Kellyanne Conway's Comey Comments
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After getting remand CBI will now try to cross-examine the statements given by accused MLA Kuldeep Singh Sengar in presence of Shashi Singh.
He said, "Some goons of Kuldeep Sengar (accused BJP MLA) are threatening villagers to keep quiet". As the rape survivor has accused the MLA and his accomplices of raping her on multiple occasion in June, 2017, UP police failed to collect any scientific evidence in the case.
In a complaint to the Uttar Pradesh Police, the victim's mother alleged that the Shashi stood guard outside the room where Sengar's raped her daughter.
The family members also criticised the national media for portraying their agitation for a CBI probe into the case as "pro-rapists" and "pro-culprits", and said the scribes were "delivering judgments without investigation".
The development came a few hours after the Uttar Pradesh government handed over the Unnao rape case to the CBI.
The father expressed satisfaction with the probe conducted so far by the state police, while vehemently opposing the plea of senior advocate Bhim Singh and Delhi-based lawyer Anuja Kapur that the investigation be transferred to the CBI.