The observation was made by a bench comprising Justice M Chockalingam and Prof R Nagendran during resumed hearing of the matter related to alleged pollution in packaged drinking water supplied in the city and other parts of the state.
The NGT, based on news reports, had taken up the issue on suo moto basis in March last.
During the last hearing, the Tamil Nadu Pollution Control Board (TNPCB) had submitted that as many as 814 units out of 967 do not have its nod for functioning.
The TNPCB had earlier submitted that a Madras High Court order related to the act stood in the way grant of approval to their units.
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Counsel for the TNPCB said that clearances from State Ground and Surface Water Resources Data Centre of Public Works Department, Directorate of Food Safety and Standards Authority and the Director of Town and Country Planning were needed.
Concurring, the Bench said NoC from all the appropriate authorities should be obtained prior to seeking TNPCB's nod.
The matter was adjourned to November 29.