The CBI, which is probing the RG Kar Hospital rape-murder case, has told a local court in Kolkata that "some false records, pertaining to the case, were created at the Tala Police Station".

The federal agency, tasked by the Calcutta High Court with investigating the killing of a junior doctor last month, also said it had CCTV footage from the police station in question, and that this has been sent to a central forensics lab in the city for examination. Kolkata Police has not yet responded.

This significant twist in the case comes after the CBI interrogated Abhijit Mondal, the officer-in-charge of the Tala Police Station at the time. Mondal, arrested on charges of tampering with evidence, and Dr Sandip Ghosh, the hospital's former chief, held over financial irregularities, are both in CBI custody.

Prime suspect Sanjay Roy - a civic volunteer with the cops, who was seen on CCTV footage entering the room in which the body was found, hours before it was - has also been arrested.

On Wednesday the agency had produced Mondal and Ghosh before the court following completion of their remand. The court subsequently sent them to judicial custody till September 30.

Last week the agency told the court it suspects a 'nexus' between the two; the CBI referred to phone calls between Mondal and Ghosh. Mondal's lawyer pointed out that given a serious crime had been reported from the hospital it was normal for the two to speak multiple times.

That point was flagged in the trial court yet again today, and the defence pointed out the CBI, though it had made these critical allegations, had not provided evidence to back its claims.

Apart from identifying those guilty of the killing of the 31-year-old junior doctor, the CBI is also investigating reports of destruction of evidence in connection with the rape and murder.

Mondal, the CBI has said, is not accused in the rape or murder, but may have played a role in the cover-up that followed. The Bengal government and police force are facing severe scrutiny in this regard, with many alleging the state is trying to protect those guilty.

The CBI is also probing a "criminal conspiracy" between Mondal, Ghosh, and Roy, pointing to the "unnecessary delay of two days" in the seizure of the clothes the latter wore on the day. This, the agency told the court, could have led to contamination of material evidence.

Among the points of order flagged by the High Court and Supreme Court (which took suo moto cognisance) is that there was a 14-hour delay between finding the body and filing a police case.

Both courts have demanded to know why the hospital administration, then led by Sandip Ghosh, did not do so immediately, which would, in turn, have ensured the police filed a FIR.

As an aside, Mondal was last night admitted to the prison hospital. Sources told news agency IANS he tripped and fell while being taken back from the court after yesterday's hearing.

Also, on Sunday the CBI also questioned another doctor - Birupaksha Biswas, allegedly close to Ghosh - in connection with the rape and murder. Biswas was reportedly part of the 'North Bengal lobby', which medics in the state say have threatened medical students in the past.

Meanwhile, on Saturday, junior doctors partially rejoined duties after striking for over 40 days to protest the killing of their colleague. They rejoined for essential and emergency services only.

They have been protesting since August 9 - which has included three failed attempts at talks with Chief Minister Mamata Banerjee - for justice for their colleague and removal of three officials, including the Health Secretary, alleging their involvement in the case.

The doctors made it clear this partial return is not an end to their agitation. "If needed, we will begin protests again," they said.

With input from agencies