Director of the Central Bureau of Investigation (CBI) Amar Pratap Singh has said the 2G scam was the most challenging case he has come across during his nearly two-year tenure as CBI chief.

When asked whether it was on account of the huge loss figure being quoted, Singh, who would be demitting office on Friday, said, "Not because of the figures but the complications involved and monitoring by the Supreme Court."

However, the CBI said it has not come across any loss figures to the exchequer because of the 2G spectrum scam.

The outgoing Director said the Rs 30,000-crore figure given by the CBI is the "indexed price of 2001".

"But we had not termed it as loss. It was a notional figure that this could have been the price," Singh added.

siddhartha.s@thehindu.co.in