The bizarre scene played out through the morning when the froth spilt over to the neighbouring road from the 445.14-acre lake, The Hindu reported.

“This is not the first time there is froth coming out of the lake. But, we have never seen it in this much magnitude… The froth has overflowed on the road and was even spraying on to oncoming vehicles and pedestrians,” said Elangovan, member of Whitefield Rising, who is working for the restoration of Varthur Lake. Eventually, a water tanker was employed by the Bruhat Bangalore Mahanagara Palike (BBMP) to spray down the froth and push it back to the lake.

Environmentalist Yellappa Reddy said the froth was due to washing machine detergents, which flowed into the lake with the raw sewage let in. “These detergents have high concentration of phosphates, which leads to lowering of the biological oxygen demand and chemical oxygen demand of the lake. This will cause aquatic life in the lake to die slowly,” he said. An officer in the Karnataka State Pollution Control Board said the froth was formed due to the reaction of detergents and toilet cleaners with warm water.

“This is a constant issue as sewage flows directly into the lake. However, BWSSB is constructing a Sewage Treatment Plant nearby, and until this is set up to treat the sewage, the problem will persist,” he said on condition of anonymity.