New Delhi: In a special operation in West Bengal's Malda district, NIA on Monday arrested 15 protesters in connection with last month's road blockades and illegal detention of judges engaged in the special intensive revision of electoral rolls ahead of the assembly polls, the agency said in a statement.NIA, which had taken over the investigation on the Election Commission of India's direction after the Supreme Court took suo motu cognizance of the acts, carried out an extensive operation in Malda district on Monday.A total of 15 persons were apprehended for their involvement in blockade of roads and illegal detention of judicial officers on duty in two separate cases. They were produced before a judicial court on Tuesday. In one case, 12 individuals, including the main accused Joshim Sk and Asmaul Sk, were arrested for detaining a lady judicial officer for about eight hours along the road between Haibatola and Amlitola, according to NIA.Three other persons were arrested in connection with the blockade of Bagmara Bridge in Mothabari block.