The special cell of Delhi Police arrested an assistant sub-inspector, a head constable and a constable of the state police late Wednesday.
The three private detectives who were also arrested are Puneet Verma, Alok Gupta and Mehraz Saifi.
According to the police, the six were initially called for questioning after which they were booked under several charges.
Earlier, police had filed a charge sheet against a constable and three private detectives in the same case. But the four were granted bail by a Delhi court May 30.
The incident came out in january this year and had created huge political furore.
(With agency imputs)