Kolkata, Dec 14 : Central Bureau of Investigation (CBI) was conducting raids and search operation at multiple locations in West Bengal, including Kolkata on Thursday in connection with the coal smuggling case. Sources said that simultaneous raid and search operation was being conducted at places like Bhawanipur in South Kolkata, Durgapur and Kulti in West Burdwan district and Malda, among others. The 13 places where the CBI sleuths were conducting raids and search operations also include the residences of two retired Central Industrial Security Force (CISF) personnel. CBI sleuths have identified huge assets disproportionate to their income. Each team of CBI sleuths was being escorted by armed personnel of the central armed police forces. Sources said that the residences and offices of those, where the raid and search operations were being conducted include those who were in the radar of the central agency for quite some time because of their close associations with Anup Maji a.k.a. Lala, a prime accused in the multi- crore coal smuggling case in the state. The CBI sleuths had been especially attentive towards the nexus between the coal smuggling kingpins and a section of the officials of CISF as well as Eastern Coalfields Limited (ECL), a subsidiary of Coal India Limited (CIL). The central agency sleuths believe that without the involvement of the ECL and CISF officials, the scam of such a magnitude could not be implemented. Earlier this year, the CBI sleuths arrested a former director of ECL and Anand Kumar Singh, a former inspector of the Central CISF in connection with alleged coal smuggling scam. Both, according to the CBI, were beneficiaries of the alleged scam and had close connections with Lala. /IANS