The agency has registered cases against BLA industries, Castron Technologies, Castron Mining, the MD of BLA, some unknown public servants and private persons, CBI sources said.
It is alleged that undeserving companies were given coal block allocations.
They said BLA was allegedly permitted to sell the coal in the open market against the principle of captive mining.
CBI spokesperson said searches are being conducted at Dhanbad, Narsinghpur (M.P.), Mumbai and Kolkata in connection with the case.