BENGALURU - Veritable walls of toxic foam have enveloped residents on the shores of two heavily polluted lakes in the Indian city of Bengaluru after days of heavy rainfall.

Videos on social media show foam as high as buildings blowing through the streets and spilling through wire fences that had been erected to keep out the foam, which is a year-around occurrence, but seldom reaches such dramatic proportions, reported The Daily Mail.

The Varthur and Bellandur lakes are notorious for spitting out mounds of bubbles that sometimes spill on to the roads, disrupting traffic. The phenomenon is caused by a cocktail of chemicals, including ammonia, phosphate and low dissolved oxygen.

But the latest development comes in the wake of the heaviest rain in Bengaluru since 1890. It is not the first time that 'clouds' of toxic foam have covered the area either. A similar incident took place in 2015 and the foam - caused then by the rain as well - ignited due to the flammable components in the toxic waste.

The National Green Tribunal has ordered that industries around Bellandur lake should be shut and heavy fines imposed on anyone dumping waste in and around the lake. However, the problem persists and efforts to clean up the lake have also failed.