Two senior Indian Police Service (IPS) officers posted at the state police headquarters are at loggerheads over the investigation into the high-profile case of alleged sexual exploitation of a former Dalit minister's daughter.

On April 11, Vinay Kumar, a 1991-batch IPS officer posted as additional director-general of police (ADG) with the criminal investigation department (CID), removed a deputy superintendent of police (DSP)-rank officer, Mamta Kalyani, from the special investigation team (SIT) constituted to investigate the allegations levelled by the survivor against Nikhil Priyadarshi, an influential automobile dealer, and others.

Vinay, who was monitoring the investigation, removed Mamta from the four-member SIT she was heading and which had another DSP-rank officer, one inspector and a sub-inspector.

Irked over his senior's decision, Anil Kishore Yadav, inspector-general of police (IG), weaker section, on Saturday wrote to Amir Subhani, principal home secretary, requesting that ADG Vinay, himself (Anil), and a top Bihar cop should be kept away from the investigation.

The survivor, who had lodged a complaint with the SC/ST police station in Patna in December last year, had alleged that the wards of several senior police officers, politicians and bureaucrats were close to Nikhil, who she alleged was involved in running a sex racket. She had provided video clips to substantiate her allegations.

Yadav, a 1996-batch IPS officer, was also monitoring the case by dint of his jurisdiction over cases involving the weaker sections of society.

He has recommended that the state government assign the investigation to a joint police team comprising a retired woman IPS officer and an officer belonging to the scheduled caste so that justice can be done to the survivor.

The reason ADG Vinay cited for removing Mamta was her not initiating action against Kumar Mrinal, whose flat was allegedly used for running the sex racket. The survivor, in her statement before the SIT, had alleged that Brajesh Pandey, then vice-president of the Bihar Pradesh Congress Committee, had tried to molest her in Mrinal's flat on Boring Road in the capital. Pandey, who has since lost his Congress post, is absconding.

Highly placed police sources, however, said the bone of contention was the charges under the Protection of Children from Sexual Offences (Pocso) Act, 2012, which have been slapped on Nikhil, his associates, and Brajesh Pandey on the recommendation of Mamta, who was the SIT chief. Based on the same recommendations, Patna High Court also directed the cops to ascertain the survivor's age.

According to documents - such as matriculation certificate, Aadhaar card and passport - the survivor has provided to the SIT, she was born in 1998 and was a minor when she was exploited. However, the accused's legal counsel submitted in court that the girl was born in 1996 - as per the records of a reputed school where she was first admitted.

The survivor, according to IG Yadav, had alleged that some senior IPS officers including a top Bihar cop were trying to shield the accused.

The survivor had alleged that the top cop's son was trying to hush up the matter because he is an old friend of Nikhil, the prime accused and son of a retired IAS officer.

ADG (headquarters) Sunil Kumar had denied the allegation against the top cop's son but promised action against the offenders, whosoever they may be.

While IG Anil refused to comment on the issue, ADG Kumar initially did not respond despite several calls and messages to his mobile phone, but later on Sunday said to call after 10pm.

The sudden removal of Mamta, a Bihar police service officer, from the SIT has created ripples in the police headquarters.

"One can well imagine the way police (read home) department is functioning these days," a senior officer said under cover of anonymity.

Another officer called it an ego clash between two titans: "Both the IPS officers have their own way of functioning. While the ADG wants to run the CID his way, the IG-weaker sections doesn't like it."

A former director-general of police, who did not want to be identified, said: "Whatever the reasons may be for the differences between the two senior police officers, one thing is sure - the development has sent a wrong message among the junior officers."