Gujarat Anti-Terrorist Squad (ATS) has arrested a man suspected to be one of the conspirators of the 2002 terror attack on American Centre in Kolkata which claimed the lives of four policemen. Following a tip-off, ATS officials nabbed Hasan Imam from Aurangabad in Bihar and brought him to Ahmadabad yesterday. ATS, in a release, said Imam was actively involved in the conspiracy. He was a member of the banned terror outfit Harkat-ul-Jihadi-e-Islam as well as Asif Raza Commando Force' formed by Aftab Ansari. Ansari was arrested by CBI in February 2002 upon his deportation from Dubai. He was the key accused in the attack on the American Centre.