The agency, which has questioned Dr Ghosh several times since it took over the case from the Kolkata Police, took the five to the court of Additional Chief Judicial Magistrate (ACJM) which admitted the petition, officials said.

The four doctors were on duty with the victim, a postgraduate trainee, on the night of the incident.

The agency had also sought approval to conduct polygraph test on the accused Sanjay Roy, a civic volunteer, who was arrested by the police a day after the incident that has created a massive uproar across the country.

The woman doctor was found dead in the seminar room of the Chest Medicine Department of the college.

The investigators are of the opinion that the “renovation work” near the place of the occurrence of the incident a few days after the rape-murder could be a “conspiracy” and it therefore needs to be investigated thoroughly.

Dr Ghosh’s mobile call and message details are under the scanner of the investigators, it is learnt. He is believed to have deleted several WhatsApp messages after the incident.

Ghosh stepped down as the principal of the RG Kar Hospital, two days after the rape and murder, citing “moral grounds”. He, however, was posted as the principal of the Calcutta National Medical College within hours, triggering a massive outrage.

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