The Central Bureau of Investigation on Tuesday wrote to the Prime Minister’s Office seeking all the documents pertaining to the allocation of the Talabira coal block to Hindalco Industries.

The PMO had a few days ago defended the decision to allocate a coal block to the company, stating that Prime Minister Manmohan Singh had approved it on merit.

The move comes after the agency filed a status report apprising the Supreme Court of the case registered against Aditya Birla Group chairman Kumar Mangalam Birla and the former Coal Secretary, P. C. Parakh, for having allegedly entered into a criminal conspiracy to facilitate partial allocation of the Odisha coal block to Hindalco about eight years ago.

The FIR registered in the case mentions the “competent authority” that granted allocation of the coal block to Hindalco. The Prime Minister was in-charge of the Coal Ministry in 2005 when the decision was taken.