The NGT bench headed by Justice Swatanter Kumar asked the Delhi government, along with the DDA and Delhi Metro, to show the extent of debris removed by them.
"You have filed affidavits before us... stating that debris from the floodplains of Yamuna have been removed. However, they (Art of Living) are saying something different. You address us on that behalf," the bench said.
The NGT's observation came after the lawyer for Art of Living told the green panel that debris already existed on the site before the event and the condition of the floodplains was "pathetic".
Earlier, an expert committee told the NGT in a report that it would need Rs 42.02 crore and many years to restore the Yamuna floodplains to the same condition before the three-day cultural event.
The NGT will hear the matter again tomorrow.