CBI sources said that Patel, an "alleged racketeer" out on bail, was found dead in a room of a lodge in Kanker, Chhattisgarh on April 28.
Singh was allegedly linked to several high-profile suspects in the Vyapam case and was being probed by the Special Task Force for his role in three cases.
It is believed that he had gone Kanker to meet his wife after which became untraceable. His body was found in a lodge allegedly run by a member of ruling party.
The probe agency on Saturday had registered a preliminary inquiry into the mysterious deaths of nine persons allegedly linked to the scam in Madhya Pradesh.
The agency has also registered 12 FIRs in connection with various aspects of Vyapam scam.
