The National Investigation Agency (NIA) has been handed over the probe into the death of Thane-based businessman Mansukh Hiren whose body was found in a creek days after a vehicle laden with explosives was parked near the Mumbai residence of industrialist Mukesh Ambani, officials said on Saturday. br br The NIA is already probing the case related to the recovery of a Scorpio SUV, parked near Ambani's residence 'Antilia', with gelatin sticks and has arrested an assistant police inspector, Sachin Vaze.