A thick layer of toxic foam has once again coated parts of a sacred river near New Delhi as the Indian capital battles an acrid and noxious smog that has settled across the city.

The white froth, a mixture of sewage and industrial waste, has formed over sections of the Yamuna River – a tributary of the holy Ganges River – which flows about 855 miles (1,376 kilometers) south from the Himalayas through several states.

The pungent foam contains high levels of ammonia and phosphates, which can cause respiratory and skin problems, according to experts. Its latest arrival has coincided with hazardous levels of pollution that have sickened many of New Delhi’s more than 20 million residents and forced primary schools and some offices to close.

A similar looking mixture has appeared in a canal in India’s southern Tamil Nadu state, according to the Press Trust of India. Video published by the news agency on Thursday shows strong gusts of wind carrying the froth onto the roads and into the paths of cars and motorcycles.