Bengaluru’s biggest lake, Bellandur lake, started frothing again on Wednesday, The Times of India reported. The toxic froth is produced as a result of untreated sewage water flowing into the lakes.

On Monday, Karnataka’s Deputy Chief Minister Parameshwara visited the lake after a report by the National Green Tribunal on May 31 said sheer callousness and indifference of the city administration had forced the lake to become the “largest septic tank of the city”.

The National Green Tribunal’s inspection commission found that the the lake’s storage capacity has reduced to 28.55%. According to the report, sewage treatment plants were available only at 496 of 873 establishments in the lake’s catchment area, The New Indian Express reported.

“Today the present area of the lake comes out as 895 acres and 19 guntas,” the report said. “On the basis of a certificate dated April 19, issued by Tahsildars, the extent of the lake was about 906 acres and 19 guntas.”

Both the Bellandur and Varthur lakes are regularly affected by froth. Residents from the area have repeatedly asked the government to take action to stop the lake from foaming. Many have also criticised the city’s civic body for failing to address the problem.

In April 2017, the National Green Tribunal ordered the Karnataka government to shut down all industrial units around the Bellandur lake. It also announced a Rs 5-lakh penalty for anyone found dumping waste in and around the lake.