The Special Investigation Team (SIT) probing Monday's Amarnath Yatra terror attack has arrested a local policeman on suspicion of aiding terrorists strike the bus on July 10, killing seven pilgrims. Claiming a major breakthrough in cracking the terror attack on a Yatra bus, the SIT has arrested a policeman and is also questioning a ruling PDP legislator in connection with the case. "The SIT is questioning a ruling PDP legislator since the arrested policeman, identified as Touseef Ahmad of state security wing, was posted on the legislator's personal security," police sources said. The policeman belonging to Pulwama district was picked up on Thursday by the SIT following a phone intercept. The intercept, according to sources, is based on the policeman's conversation with a handler of the Lashkar-e-Taiba. The state police has said the attack was carried out by the LeT outfit and a Pakistani national, Muhammad Abu Ismail, along with another foreigner and three local militants were involved in the attack."The police are trying to ascertain as to who provided the details about the movement of the vehicle during the Yatra," the sources said. Also watch: So far, around 20 persons have been detained for questioning by the police in connection with the investigations into the terror attack.