DRI sources said the investigation against Rahat and fourof his associates was nearing completion and a case underForeign Exchange Management Act (FEMA) is likely to be filed.
Rahat was quizzed for about three hours today, the thirdtime since his detention on February 13 at Indira GandhiInternational Airport here.
The DRI officials also interrogated two foreign exchangedealers in Mumbai today in connection with the matter.
The 37-year-old singer is likely to be questioned againtomorrow.
Besides Rahat, his manager Maroof, owner of an eventmanagement company Chitresh Shrivastava, and two employees ofMumbai-based Foreign Exchange firm were detained andquestioned at length about the source of the money.
Rahat was detained when he, along with his 16-membertroupe, was on his way to Lahore via Dubai.
Soon after their detention, searches were conductedsimultaneously on the premises of "Eyeline Telefilm andEvents" in Mumbai, owned by Chitresh, elder brother ofbollywood singer Aadesh Shrivastava.
Sources privy to the investigations claimed that thesleuths found Rs 51 lakh in cash which was seized besides somedocuments.
As per norms, no one can carry beyond USD 5,000 in cashand USD 5,000 in other instruments. The person has to declarethe amount if he is carrying more than this to the CustomsDepartment.
Meanwhile, authorities here have extended singer''s visato 10 more days after its expiry on February 14, sources said.
Khan is rated as a one of the top playback singer ofHindi film industry who has several hit numbers to his credit.
He won the Filmfare Award for Best Male Playback Singer thisyear for ''Dil To Bachcha Hai Ji'' from the movie ''Ishqiya''.