In a letter to Chief Minister Shivraj Singh Chouhan, the Congress General Secretary has said, "Some officials, including MPPEB exam controller Pankaj Trivedi and Officer on Special Duty (OSD) O P Shukla, have already been arrested in connection with the scam.
"However, former minister Laxmikant Sharma and mining baron Sudhir Sharma have so far not been apprehended," he said in the letter.
The scam is being probed by Madhya Pradesh Special Investigation Team (SIT).
"Despite clear proofs, attempts are being made to save Laxmikant Sharma, Sudhir Sharma and Dr Ajay Mehta. I urge you to order a CBI inquiry into the scam as some people are pointing their fingers at you also," Singh said.