CBI sources said a team of four officers visited the ministry in connection with its two enquiries to look into the issue of missing files on coal block allocations from the Coal Ministry.
The agency sources said they are looking into role of two influential persons who are named as accused in FIRs registered by the agency in the coal block allocation scam.
The agency had registered last month two enquiries in connection with the missing files. The sources said 15-18 crucial files which are related to coal block allocations in different batches are not traceable and it is affecting the agency's probe.
CBI has split its enquiry in two parts-- files relating to allocations done during the period spanning from 2006-09 in which CBI has registered 13 FIRs so far and files related to the period between 1993 and 2005 in which no FIR has been registered, the sources said.
They said the agency decided to proceed with the preliminary enquiry as there was not enough material to register a regular case or FIR.
During the analysis of documents and interactions with Coal Ministry officials, CBI found that some of the crucial files are not in existence.