CBI personnel reached Sengar's residence in Lucknow in the early hours today and took him for questioning at its office in Lucknow, officials said.
The CBI took over the case from a Special Investigative Team following a request to the Centre from the Uttar Pradesh government.
His comments come a day after a senior Bharatiya Janata Party (BJP) leader in Uttar Pradesh had claimed that the Chief Minister had chose to arrest rape accused MLA Kuldeep Singh Sengar but his decision was changed after the intervention of a "prominent person". Her father was arrested and later died in custody. CBI officials also took over records such as treatment prescription, ultrasound reports and details of the post-mortem which was conducted by a panel of doctors.
The victim's father died in judicial custody nearly a week after he was reportedly thrashed by the MLA's brother and others. The case has been transferred to CBI finally after pressure mounted up.
What seems to have compounded trouble for the Yogi government is the fact that the Unnao rape case has come simultaneously with the horrific rape and murder of an eight-year-old girl at Kathua in Jammu.
Addressing reporters on Friday, Adityanath said that his government will not compromise on the case irrespective of the position of the accused.
The first FIR pertains to the alleged rape of the girl in which Sengar and Shashi Singh have been named as accused. Subsequently, the victim's father was booked by the police under the Arms Act on April 3 and put in jail on April 5.
The girl tried to set herself on fire outside the Chief Minister's residence on Sunday, claiming inaction in the gang rape case.
Her uncle also said he was "very happy" to know about the MLA's arrest, and said he was eager to depose before the CBI as "to speak the truth, we don't need to recall much".