Residents claim that sewage water often finds its way into the lake, cutting down oxygen levels drastically and causing the fish to die.

"Recently it rained heavily, so you can see that there were lot of sewage sludge and plastic again that has entered into the eight acres plus Ulsoor Lake. So, again you can see that there's mass fish deaths," said Yakub, a local.

The dead fish were seen floating on the lake's surface along with plastic bottles and garbage.

A team of pollution board was rushed to the spot. Pollution board members collected samples of the lake water which will be sent for testing to ascertain the exact cause of the deaths.

"We are collecting the samples. It will be investigated and the report will be submitted to our head office in Delhi and MoEF (Ministry of Environment and Forests)," said Tirumurthy, a member of the board.

This is the second time in as many months that thousands of dead fish have been seen around the lake, leading to a strong stench in the area.

The incident comes amid ever-growing concern among environmentalists about the rising levels of pollution in lakes across Bengaluru. Last year, residents were left shocked when flames were seen in thick froth floating on Yemlurlake. (ANI)