Pictures and videos showing devotees offering prayers in the Yamuna on Chhath Puja with toxic foam floating on the surface of the river have triggered scare and outrage.
Visuals from Tuesday again showed devotees praying in the river with toxic froth all around.
The images have also sparked a political slugfest between the ruling AAP and the BJP in Delhi.
While the BJP leaders alleged that the AAP government did not allow Chhath celebrations on the Yamuna banks to hide the "pathetic" state of the river, the AAP leaders blamed the governments in Uttar Pradesh and Haryana for the frothing in the river.
The 22-kilometre stretch of the Yamuna between Wazirabad and Okhla, which is less than 2 per cent of its length of 1,370 kilometres from Yamunotri to Allahabad, accounts for around 80 per cent of the pollution load in the river.
The presence of phosphates and surfactants in untreated sewage from Delhi, Haryana and Uttar Pradesh is a major reason behind frothing in the river, according to experts.
AAP leader and Delhi Jal Board Vice Chairman Raghav Chadha claimed that Haryana and Uttar Pradesh have been releasing around 155 million gallons of untreated wastewater a day in the river through Najafgarh and Shahdara drains.
BJP MP Manoj Tiwari, who rode a boat in the foam-covered Yamuna, alleged that the AAP government did not allow Chhath Puja on its banks because it wanted to cover up the frothing in the river caused by high pollution load.