Kolkata/IBNS: Four colleagues of the 31-year-old doctor, who was raped and murdered in Kolkata's RG Kar Medical College and Hospital, will be put through the polygraph test as according to the Central Bureau of Investigation (CBI) their statements are contradicting each other, media reports said.

These include two first-year postgraduate trainees, a house surgeon, and an intern.

NDTV quoting sources in the central agency reported that it doesn't appear that the four doctors were involved in crime, but the CBI wants to check if they played a role in tampering with evidence or were part of a conspiracy.

The investigators have also pieced together the sequence of events the night before the trainee doctor was brutally and killed.

According to Kolkata Police's timeline of events, one of these doctors saw the victim's body in the seminar hall around 9.30 am the next day and alerted the authorities.

All these four doctors have been questioned by the Kolkata Police before the CBI took over the probe.

The CBI has already received permission to conduct a polygraph test on RG Kar Hospital's former Principal Sandip Ghosh and four other doctors.

What has CBI found?

The CBI has found fingerprints of two of these four doctors in the third-floor seminar room where the body was found.

A CCTV camera had captured the house surgeon going from the first floor to the third floor that night.

The house surgeon has said he went to the third floor at 2.45 am that night. The intern was on the third floor and had spoken to the victim that night, the CBI has reportedly found.

What happened that night?

According to the NDTV sources, the victim and two first-year postgraduate trainees had dinner around midnight.

Then they went to the seminar room and watched Neeraj Chopra's javelin event at the Olympics. Around 2 am, the two colleagues went to the sleep room where doctors on duty rested.

The victim stayed back in the seminar room. The intern said that he was in the interns' room. All these three rooms -- the seminar hall, the sleep, and the interns' room are located close to each other on the third floor.

What followed the morning after?

Around 9.30 am, one of the postgraduate trainee doctors, with whom the victim had dinner the night before, went to look for her before the ward rounds began.

He found "her body in motionless state from a distance", the Kolkata Police timeline says. He then informed his colleagues and senior doctors who alerted hospital authorities.