The Central Bureau of Investigation (CBI) said Additional DG (Home Guards) AK Jain, who was to be grilled by the agency, is missing since 72 hours.
Liquor mafia Dara Singh was allegedly killed in a 'fake enciunter' by the police in Jaipur on October 2006.
Based on Singh's family's plea, the Supreme Court handed over the case to the CBI in April 2010.
The investigating agency has arrested four cops in connection with the case so far.