The search operations were based on an FIR filed on Friday, which named two general managers, two other officials, and the chief security officer of ECL, according to reports.
The agency had registered the case on Friday against accused Anup Manjhi and other unidentified people including some employees of the ECL, Railways, and CISF personnel, according to a report by PTI.
The other three states where the raids were being conducted are Uttar Pradesh, Jharkhand, and Bihar.
In West Bengal, besides Asansol and other spots, searches are on in Durgapur, Raniganj in Burdwan district, and Bishnupur in the South 24 Parganas district. The agency has registered a case for alleged illegal mining and theft of coal from ECL's Kunustoria and Kajoria fields.
The income tax department was investigating Anup Majhi, the alleged kingpin of the illegal operation around the same time when Union Home Minister Amit Shah was on a two-day visit to Kolkata. In response to a question at a press meet, Shah asked, "Why is Chief Minister Mamata Banerjee so concerned about raids against 'Lala'?"
Earlier, Mamata Banerjee had remarked at a press meet about the raids by central agencies in West Bengal coinciding with the Home Minister's visit.
The CBI has also cracked down on a cattle smuggling case in West Bengal in which the alleged kingpin, Enamul Haq, a resident of Murshidabad district, has been arrested. He is on interim bail after testing positive for COVID-19.