A team of National Investigation Agency (NIA) officials on Friday afternoon took Indian Mujahideen's (IM's) founder member Yasin Bhatkal to Delhi from Patna after his interrogation for several hours in Bihar's East Champaran district (Motihari) and state capital Patna.According to sources, Bhatkal has told his interrogators that the headquarters of the terror outfit is located in Pakistani city Karachi.