A senior official of the State Intelligence Branch (SIB) said primary investigation found that Galib visited some madrasas of North 24 Paraganas, Murshidabad and Malda districts several times.

SIB officials said neither Galib nor any of his associates visited the madrasas with valid travel documents.

"But when Galib visited Aligarh University in Uttarpradesh for his research work, he always carried proper visa," said an official.

Galib is known among the teachers and students of the university, he said, adding that the SIB is investigating into Galib's possible connections with Student Islamic Movement of India and Jamiyat-ul-Mujahideen, two outfits of India.