CBI is seeking from the Coal Ministry 257 files related to coal blocks allocation which have gone missing thus hampering agency's probe into alleged irregularities.
Out of 257 files, nearly 150 are related to the period between 1993 and 2004 in which 45 coal blocks were allocated, agency sources said.
They said some of the missing files are related to 13 FIRs registered by CBI in connection with allocations done during 2006-09.
"We have written to Coal Ministry in May seeking files related to coal allocation scam. We have not received any response from them," CBI Director Ranjit Singh told reporters.
The sources said their efforts to conclude the probe into 13 FIRs have come to a halt as several records sought by the agency about beneficiary companies are in these files which are not traceable.
They said the probe is getting affected as the allegations of misrepresentation of facts against the beneficiaries and favours given to them cannot be substantiated without the files related to allocations made.
These files carry crucial documents like application forms, supporting documents, minutes of the screening committee meetings, objections raised by officials and other records which are crucial for the CBI for proving its case.
The sources said the files are not only related to the beneficiaries' records but also the companies which were rejected thus giving alleged wrongful edge to the companies which were finally allocated the mines.
The present figure of 257 missing files may go up, they said.