MUMBAI, June 27 -- What prompted Bilal Teli, 22, to attend lectures and stay on campus at the Indian Institute of Technology Bombay, until an alert employee called his bluff? Teli, who hails from Mangaluru, was not a student of the premier engineering institute and yet he managed to deceive lecturers, students and campus security for 19 days. Teli was nabbed on June 17 but, even a week after questioning, police claim to have made little headway in the case. The only leads they have are digital - the 21 email addresses Teli was using and phone calls made through digital apps, which they hope will help them uncover the motive for his stint at the IIT campus. On Thursday, a local court remanded Teli to the custody of the Crime Intelligence Unit (CIU) of the crime branch of the Mumbai Police, for further investigation. Police said Teli has been evasive, especially with regard to why he was using as many as 21 email addresses. Teli has also refused to reveal who he was talking to on calls made via digital apps. "We are trying to extract data from his laptop and mobile phone to find out who he was in touch with and on whose instructions he was staying on the IIT-B premises illegally and attending lectures. His movements on the institute campus appear suspicious," said a senior police officer. All Teli has said is that he has a diploma in information technology (IT), which he secured after Class 10 in Mangaluru. He also claims he has relatives in Surat, police said. Interrogation has helped police piece together a timeline, which suggests that Teli arrived at the IIT-B campus on May 27, to ostensibly attend a day-long study programme. He remained on the campus, attending lectures and sleeping on couches in common areas and vacant hostel rooms, at night. On June 4, Shilpa Kotikal from the IIT's Credit Department raised an alarm, saying that an unidentified man had entered her office without authorisation. When she asked him to produce his ID card, he disappeared. Kotikal then checked the CCTV footage and shared images of Teli with campus security, who failed to locate him at the time, said a police officer. Teli left the IIT-B campus on June 7 and headed for Surat, returning on June 10. He proceeded to attend lectures on artificial intelligence and robotics for a week, and was eventually nabbed by campus security on June 17. Teli was nabbed after Kotikal noticed him in lecture hall LH-101, attending a class. The IIT Quick Response Team (QRT) detained Teli and handed him over to the Powai police. An FIR was registered on June 19, and Teli was formally arrested on June 24, on charges of trespassing. During this time, his father, a garments businessman, arrived in Mumbai, and was questioned by the police. For now, the 22-year-old suspect maintains he was at the II-BT campus for a day-long study programme and didn't want to leave as he wanted to keep attending lectures. Police, for their part, say his actions are suspicious and are hoping to uncover the motive for his stay at the premier institute....