"That is the fundamental question (source of money) which we have been asking and this has not been answered by the agencies involved in the probe," a bench comprising justices B Sudershan Reddy and S S Nijjar said while expressing their dissatisfaction over the probe.
The Bench said it was favouring the constitution of SIT as there was no substantial progress in the investigation into the source of money.
"The manner in which it (investigation) has proceeded since 2008 makes it clear that there has not been substantial progress in the investigation. The speed at which the investigation ought to have been done has not been done," it said.
"Since 2008, you have known that certain individuals for years have some kind of money abroad. Instead of looking into that, you talked about double taxation treaty and this treaty and that treaty. Simple questions you could have asked those individuals were that from where you have got that money which you have so far not answered," it said.