In an emergency hearing, the National Green Tribunal (NGT) pulled up the Karnataka government on Thursday for failing to contain the frothing in Bellandur lake.
The State argued that the situation was unforeseeable because of cloud burst.
The lake started frothing after the record rainfall on August 15 and 16, with toxic froth increasing in height. Namma Bengaluru Foundation, which is fighting the case against the government, presented audio and video clips of the plight of those suffering due to the chemical foam.
The State has been asked to respond by August 22. Earlier in February, NGT had issued suo motu notice to all civic agencies after a fire broke out in the middle of the lake.
The tribunal has asked the government how many storm-water drains it has cleared, and how much solid waste has been collected from the lake.
It also sought information on where the collected waste has been taken and what preventive steps were being put in place to ensure this does not continue.