The Central Bureau of Investigation on Thursday filed a charge sheet against 52 people in connection with malpractice in the All India Post Graduate Medical Entrance Examination.

Some candidates received answers through SMSes and phone calls.

During the investigation, 11 people including Ravi Kannan, Vijay Kanna and Baskar, all doctors at JIPMER in Pondicherry, Satish Kumar of the Madurai Medical College and Professor Kattimuthu of the Presidency College were reportedly identified as key conspirators.

The charge sheet named the candidates who received answers through SMSes and voice calls and secured ranks on that basis, 'thereby deceiving the All India Institute of Medical Sciences and depriving other candidates who would have been otherwise in the merit list', the CBI said in a statement.

The CBI's anti-corruption wing registered a case in March on the basis of a complaint received from the Union health and family welfare ministry.

The analysis of OMR (optical mark reader) sheets of the candidates who appeared from Tamil Nadu in the All India Post Graduate Medical Entrance Examination had revealed a similarity in the pattern of answers and the methodology adopted by them, the release said.

According to the CBI, a pen scanner and a docupen, was used to scan the question paper with the help of two candidates in two different examination centres.

The questions were then downloaded through a laptop and answers were prepared with the help of doctors who had assembled in a hotel room in Chennai.

The answers were then sent through SMSes and voice calls to the candidates, the CBI said.

Following disclosures made by the accused, the laptop, a printer, cell phones, SIM cards and cash to the tune of Rs 31.68 lakh was seized.