The PMO said CBI is free to investigate the case as it may have got hold of some documents post-allocation.
"It is recognised that this allocation (of Talabira coal block) is subject to an ongoing investigation. No impediment is being placed on CBI to continue the investigation and seek fresh information which may have a bearing on the case," the PMO statement said.
"The investigation on this and other matters must take their normal course under the law," it added in the statement issued in view of "extensive media coverage" on the matter.
Giving the sequence of events, the PMO said Singh had received a letter dated May 7, 2005 from Kumar Mangalam Birla requesting allocation of Talabira-II and III coal blocks in Odisha to Hindalco for its 650MW captive power plant in its integrated aluminium project in Sambalpur and for a 100MW captive plant for the expansion of its Hirakud aluminium plant in Odisha.