Guwahati, Aug 24 : At least 1.5 kg of narcotic substances valued at around Rs 7 crore were seized by the Assam police in Cachar district on Wednesday. The Superintendent of Police in Cachar, Numal Mahatta, told IANS, 'Acting on a tip-off, an operation was conducted near the National Institute of Technology (NIT) in Silchar in the wee hours of Wednesday. During the checking, 1.5 kg heroin was found kept hidden in 104 soap boxes in a vehicle.' Mahatta said that as per the initial investigation, it was found that the consignment of the narcotics was illegally transported from Churachandpur district in Manipur to Cachar via Mizoram's Champai. According to the officer, the seized drugs are valued at least Rs 7 crore in the international market. Four persons -- identified as Mamang Haokip (36), Haobem Haokip (30), Henboi Haokip (39), and Gogou Paite (30) -- have been arrested in connection with the case. Mamang, Henboi and Gogou hail from Churachandpur in Manipur, while Haobem is a resident of Manipur's Kangpokpi district, Mahatta said. Earlier on Sunday, in two separate operations, Assam police in Cachar district had seized a substantial quantity of narcotics valued at around Rs 5 crore. /IANS