Indian investigators would join their FBI counterparts on Monday to question David Coleman Headley, nabbed by FBI for plotting a major terror attack in India at LeT's behest, as fresh inputs indicated that he was planning to visit Pakistan this month.

The investigators from IB and RAW are also expected to probe the terror-drug nexus as it has come to light that Headley was charged by a federal court in New York in 1997 with smuggling heroin to the US, according to court documents accessed.

One of Headley's cousins, Farid Gilani of Philadelphia, told the Chicago Sun-Times that he spoke to Headley over the phone about a month ago. "He was supposed to come (and) visit me, but he never came," Farid Gilani was quoted as saying. "He said 'I am going back home to Pakistan."

Court papers said Headley, alias 'Daood Gilani', was planning to go to Pakistan this month, before which he was nabbed by the FBI.

49-year-old Headley was arrested on October 18 along with Tahawwur Hussein Rana, a Canadian citizen of Pakistani origin, by FBI at Chicago's O'Hare International Airport before boarding a flight to Philadelphia, intending to travel to Pakistan.

According to the sources the Indian investigators would like to solve the 'Rahul' puzzle, the FBI is keen to gain from the Indian expertise in quizzing known LeT-linked terrorists and acquaintances.

A mysterious 'Rahul' appeared to have been the prime target of Headley, who had made several trips to India and intended to stay in the country for some time -- two to four weeks -- to execute the Lashkar-e-Taiba plans, according to US investigators.

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