CBI sources said some of these companies had got coal blocks during 2006-09 despite lacking some criteria in allotment parameters, while others had allegedly violated allocation norms by changing their ownership patterns.
The central agency is likely to write to these companies seeking their clarifications on the issues of allocation and changes in ownership, they said.
The sources said they have completed first round of scrutiny and eight companies have appeared to be in suspicious category.
Although there were a large number of files to be scrutinised, they are looking to complete the preliminary enquiry in the case within a period of two months, the CBI sources said.
The probe agency had registered two preliminary enquiries in connection with the case referred to it by the Central Vigilance Commission (CVC).
1,422 applications for 64 coal blocks were received by the Coal Ministry between 2006 and 2009 from 146 private companies and all these documents have to be scrutinised, they said.
The CBI had initiated preliminary enquiries in connection with the alleged irregularities in the utilisation and allocation of coal blocks allocated to private companies between 2006 and 2009.
