First Mumbai Police, then CBI, ED and Narcotics Bureau. Will NIA be the next agency to join the Sushant Singh Rajput case investigation? The Hindustan Times has reported that after the central government's clearance to NIA to investigate drug related cases, the agency is likely to become the fourth federal agency to get involved in the case. The death of Sushant Singh Rajput has turned into a major political battle ahead of the Bihar polls and has also snowballed into a major probe into drug use in the film industry.