The companies include some of the biggest names in the sector as also some state electricity boards and central power utilities which have have come under the scanner of the Directorate of Revenue Intelligence (DRI).
The agency has found that certain importers of Indonesian coal were artificially inflating its import value against the original price, the sources said.
Intelligence developed by the agency further indicated that while Indonesian coal was directly imported from ports there to importers in India, the import invoices were routed through one or more intermediaries based in Singapore, Dubai, Hong Kong, British Virgin Islands among others for the purpose of artificially inflating its value.
The investigation conducted by the agency found that the inflated invoices received in India were found to have been issued by intermediary invoicing agents who appear to be either subsidiary companies of Indian importers or their front companies.
The alleged artificially higher prices of coal were then passed on to electricity consumers, they said.