Kolkata | The parents of the doctor, who was allegedly raped-murdered at RG Kar Medical College and Hospital last week, told the CBI that several interns and physicians from the hospital might be involved in the crime, an officer said on Friday.

The parents also provided the central agency, which is investigating the case under an order from the Calcutta High Court, with the names of persons they suspect to be involved in their daughter's murder at the state-run hospital.

"The parents told us that they suspect the involvement of multiple persons behind the sexual assault and murder of their daughter. They have given names of a few interns and doctors who worked with her at the hospital," the CBI officer said.

The agency is prioritising the questioning of these individuals and officers from Kolkata Police who were part of the initial investigation. "We have identified at least 30 suspects and have started questioning them," the officer added.

On Friday, the CBI summoned a house staff member and two post-graduate trainees who were on duty with the doctor the night she was murdered.

The agency also escorted the former hospital principal, Dr. Sandip Ghosh, for questioning.

Dr. Ghosh, who resigned two days after the body was discovered, had expressed fears of being attacked, prompting his lawyer to seek protection from the Calcutta High Court. The court directed him to approach a single bench.

As a part of their investigation, the CBI officers also took the arrested accused for a reconstruction of the crime scene, he said, adding that 3D tracking was also conducted at the seminar hall of the hospital.

The body of the post-graduate trainee was found in the RG Kar Hospital's seminar room on August 9. Police arrested a civic volunteer the next day in this connection.