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.

The sources said that diversion of the land is in alleged violation of the laid-down norms.

The Forest Advisory Committee (FAC), which comes under environment ministry, allegedly ignored the fact that there was no wildlife management plan for the forest.
The lack of a wildlife management plan was the reason why FAC had earlier deferred the decision but, during the tenure of Natarajan, the diversion was allegedly given a go-ahead despite there being no change in the ground situation, the sources said.
Forest officers in their reports had told the Government of India that the proposed mining lease area has been notified as the core area of the Singhbhum Elephant Reserve.

They had also said that the area is rich in biodiversity with 107 tree species found in a sample plot.
The report had also said that Saranda forest was an important habitat for wild elephants and a number of elephant corridors located in the area link the habitat with the adjoining forests of Jharkhand and Odisha.
"Any increase in mining operations in this area is likely to have an adverse impact on elephants and other wild animals," the report said.
CBI sources said despite the ecological importance of the forest, the land diversion was allowed by environment ministry.
They said the agency will soon be examining environment ministry officials to know what were the changes in the circumstances which led to the permission being given for the diversion of the ecologically-sensitive area for mining operations.

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