A bench headed by NGT Chairperson Justice Swatanter Kumar said a detailed affidavit enumerating steps being taken to clean the river should be filed.
The green panel also asked the city government and the Delhi Jal Board (DJB) to submit a status report on compliance of its directions on the execution of phase-I of Yamuna cleaning work.
The first phase is on control and prevention of pollution at Najafgarh and Delhi Gate drains.
Thousands of idols of Ganesha (the elephant god) made of plaster of Paris and coated with toxic chemicals such as mercury, cadmium, lead and carbon were immersed in the Yamuna on the occasion of Ganesh Chaturthi which commenced late August.
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The NGT was hearing a plea filed by environment activist Akash Vashishta seeking directions for steps for cleaning the banks of the river which, he said, were completely choked with dumped waste.
The bio-oxygen demand of the river, a measure of organic pollution, reached "dangerously high levels" during Ganesh Chaturthi, it said.
Stressing that the river was dying a slow death, the petition said the continuous and unabated immersion of idols into the Yamuna have caused complete choking.
The river has been turned into a virtual dumpyard of waste, the plea, filed through advocate Upama Bhattacharjee, said.
It has sought directions for a complete bar on dumping of waste and an action plan to deal with idol immersion in the entire National Capital Region (NCR).
"Idol immersion should be allowed only of the ones which are made from bio-degradable material and not plastic/plaster of Paris. Only those colours should be used on the idols which are environment-friendly," the bench had then said.