Prime Minister Manmohan Singh held direct charge of the Coal Ministry from 2006-2009.
Under attack for losing important documents that explain how coal fields were allocated to private firms, the government today told the Supreme Court that seven files remain missing and that it is trying to locate them.
In an affidavit, the government said that the CBI, which is investigating "Coal-Gate" - allegations of massive irregularities in mining licenses, needs 43 files, of which all but seven have either been located or delivered to the CBI.
Two weeks ago, the CBI said it had written to the Coal Ministry seeking 225 files.
The government acknowledged that seven files had disappeared, leading to accusations of "destruction of evidence" by the opposition, and a demand for a clarification from the Prime Minister.
Dr Manmohan Singh held direct charge of the Coal Ministry from 2006-2009. Some of the files missing relate to allocations of coal fields during this period.
The government said today that an inter-ministerial committee assigned to track the missing documents has met thrice and hopes to locate the files within a month.
The CBI has, meanwhile, asked the Supreme Court for permission to share its updated report on its investigation with the prosecutor handling the case. In May, the Supreme Court ruled that reports must be kept confidential after the CBI admitted that officials in the Law Ministry and Prime Minister's Office had vetted a report before it was shared in court.
The CBI also said that it believes it does not need the government's permission to interrogate senior officials. The Supreme Court had said that when it monitors an investigation, the government does not need to be consulted on the questioning of its officers; the government had objected to this.