"Nagar, accused of raping and assaulting a 35-year-old woman, was arrested around 6 p.m. after about six hours of examination. He is being taken for medical examination and then shall be detained in the CBI's Jaipur office," said a CBI official.
"Nagar will be produced in court tomorrow (Saturday)," he said.
The Sodala police station booked Nagar for allegedly raping and beating up the woman Sep 11 after calling her to his official bungalow in Jaipur on the pretext of giving a job.
The CBI Oct 9 took over the probe from the Rajasthan Police.
Following registration of the case, Nagar resigned as minister of dairy, khadi and rural industries.
Earlier, the CBI team conducted forensic examination of Nagar's official residence. The team also recorded the victim's statement at her residence.
Last month, the Congress high command suspended Nagar from the party.