The father of the doctor, who was allegedly raped and murdered in the RG Kar Medical College and Hospital last month, informed the CBI that he had talked with his daughter over the phone a few hours before her death and urged the agency to "save" call records of her phone, a source said on Thursday.

In a letter to the CBI, the father also requested the officers to secure the CCTV footage at the hospital, primarily those on the floor of the seminar hall, where the body of his daughter was found on August 9.

"The father of the deceased wrote a letter to us with a request that we save the call records," the CBI source said.

The central agency officer said that the letter, along with the status report of their probe of the rape-murder case at the hospital, was shared with the Supreme Court on September 17 during its hearing.

In his two-page letter, the father, who expressed his "helplessness and anxiety" over the investigation of his daughter's death mystery, has also requested the CBI officers to recover the duty chart to find out who all were on duty on that August 8 night along with his daughter.

The parents had also told the CBI that several interns and physicians from the hospital might have been involved in the crime.

A day after the medic's body bearing severe injury marks was found on August 9, a civic volunteer was arrested by the Kolkata Police in connection with the case.

On August 13, the Calcutta High Court ordered the transfer of the probe from the Kolkata Police to the CBI, which started its investigation the next day.

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