CBI sleuths on Thursday collected the dental impression of Sanjay Roy, arrested prime accused in the rape-murder incident at state-run RG Kar Medical College and Hospital, as part of their investigation, an officer said.

Roy's dental impression, which could play a vital role as evidence in the case, was collected during a questioning session by the central agency detectives at the Presidency Correctional Home here, he said.

"There were bite marks on the body of the woman and the post-mortem report has mentioned those. Our idea is to match those with the accused's dental impression," he told PTI.

Roy, a Kolkata Police civic volunteer, is the only person to have been arrested in the case so far.

The CBI is probing the incident following the Calcutta High Court's directive.

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