The Central Bureau of Investigation has started looking into an alleged scam worth Rs 487 crore, involving the over-valuation of inferior quality of coal imported from Indonesia through collusion of officials of state-run companies.

The CBI filed cases against AR Buhari, the promoter of Coastal Energy Private Limited, and unidentified officials of thermal power company NTPC, Metals and Minerals Trading Corporation and Aravali Power Company, PTI reported. They are accused of criminal conspiracy and cheating and also charged under provisions of the Prevention of Corruption Act.

The investigation follows the probe by Directorate of Revenue Intelligence, which showed that imports between 2011-’12 and 2014-’15 were billed higher than their value, officials said on Tuesday.