The CBI on Friday summoned four post-graduate trainee doctors of RG Kar Medical College and Hospital for questioning as it intensifies its probe into the brutal rape and murder of a trainee doctor at the state-run institution, sources said. The four doctors have been summoned to the CBI’s office in the CGO complex, Saltlake.

Sources said the trainee doctors would be questioned about the sequence of the events on the night of the incident.

The semi-naked body of the 32-year-old trainee doctor was found on August 9 in the seminar hall of the government-run hospital. A civic volunteer, Sanjay Roy, linked to Kolkata Police has been arrested even though the possibility of multiple individuals being involved has not been ruled out.

On Thursday, the CBI questioned three batchmates of the trainee doctor who were on duty on the night of August 8. The former head of the chest medicine department of the hospital was also questioned by the central probe agency.

The officer-in-charge of the Tala police station, under the jurisdiction of which the hospital is located, was also questioned by the CBI.

A CBI team also visited the residence of the victim and spoke to her parents. The sleuths took note of the time they received the call from the hospital on August 9 and also asked them about their daughter’s friends.

The CBI officers have also sought the call detail record of Sanjoy Roy. “We are also looking into data consumed by his mobile to ascertain whether he made any video or internet voice calls,” an officer told PTI.