Kolkata, Sep 21 (IANS) Controversial former senior resident doctor attached to the Pathology Department of the Burdwan Medical College & Hospital Birupaksha Biswas, who is a confidant of former R. G. Kar principal Sandip Ghosh, has arrived at the CBI's office in Kolkata on Saturday for interrogation related to the August 9 rape and murder case.

Biswas was summoned, a day after the special court in Kolkata extended the CBI custody of former SHO of Tala Police Station Abhijit Mondal and Ghosh.

On Friday, CBI also appealed to the court for a narco-analysis of Ghosh and a polygraph test for Mondal. A decision on the matter is still awaited.

Biswas, a close confidant of Ghosh, was suspended by the West Bengal Medical Council on September 7, along with two other doctors the erstwhile resident medical officer (RMO) of the Radiodiagnosis Department of Burdwan Medical College Avik De and junior doctor of Midnapore Medical College & Hospital Mustafizur Rahaman Mallick.

The common allegation against all three of them had been using their proximity with Ghosh and the leaders of the Trinamool Congress to "threaten" and "harass" other junior doctors at their respective workplaces.

Earlier on September 5, the West Bengal Health Department had announced the suspension of both Dey and Biswas from state medical services.

Ghosh is currently facing a probe by central agencies on two charges, the first being the rape and murder case and the second being the financial irregularities at R.G. Kar.

On Friday, a special court in Kolkata extended till September 25 the CBI custody of Ghosh and Mondal.

Both Ghosh and Mondal have been accused of misleading the initial phase of the investigation into the incident conducted by the Kolkata Police before the Central Bureau of Investigation (CBI) was handed the charge of the probe by the Calcutta High Court.

Ghosh and Mondal are also accused of tampering with the evidence during the initial stages of the investigation.