CBI sources said the agency may also include in the FIRs several senior environment ministry officials who were part of the clearance process.
They said the agency may also call Natarajan for questioning after registering the FIRs in these cases.
The sources said there were alleged irregularities in the allocation process as the environment ministry changed its position a number of times before the land was cleared in 2013.
The inquiry has been initiated against unknown officials of JSPL and environment ministry for alleged irregularities in the diversion of Saranda forest land in Jharkhand between 2007-13, they said.
Records with the state government and the Centre are being examined by CBI, the sources said.
They said that 512.43 hectares of ecologically-sensitive Saranda forest land in West Singhbhum district of Jharkhand were diverted for the Ghatkuri Iron Ore mining lease project in favour of JSPL.
The diversion of the land was questioned by several environment activists as well as the MB Shah Commission.