Officials said Sengar, who was brought to the CBI's office on Naval Kishore Road in Lucknow about 5 am, was taken into custody after intense questioning for 16 hours by a team of investigators. The BJP MLA was interrogated for a long time before he was arrested by the CBI.
The first FIR pertains to the alleged rape of the girl in which Sengar and Shashi Singh have been named as accused.
During the meeting, they took details of the "line of treatment" given to victims father when he was rushed to the hospital buy the police with 18 wounds and a ruptured intestine, due to beating by the lawmaker's brother and their close aides along with the police.
With possibility of arrest of BJP MLA Kuldeep Singh Senger, the Special Investigation Team (SIT) tonight submitted it's interim probe report to the Uttar Pradesh government.
The CBI has registered three cases against Sengar in regard to the crime he allegedly committed past year. The 2nd is in rioting, in which 4 people have been taken into custody.
The court also directed the CBI "carry out further investigation/ re-open the investigation of the crime (rape) registered on 20 June 2017, alongwith other three crimes".
The final report can either be a closure report or a chargesheet.
On the opposition parties accusing the UP government for "delaying the MLA's arrest", Singh referred to the former chief minister Akhilesh Yadav having "shielded rape accused minister" Gayatri Prajapati.
In February, the girl's family moved court seeking to include the MLA's name in the rape case.
The police custody was approved under the Protection of Children from Sexual Offences (Pocso) Act on charges of raping the 17-year old girl.
The woman had attempted suicide outside the residence of chief minister Yogi Adityanath, triggering a massive political row over women's safety in Uttar Pradesh. Her father died in judicial custody the next day, nearly a week after he was reportedly thrashed by the MLA's brother and others.
Sengar, a four-term MLA, enjoys vast clout cutting across party lines in the rural areas around Unnao district, a semi-urban area about 70 km from Lucknow. The third one relates to Sengar's brother Atul Singh, who claimed that he was attacked by the victim's father.