Fish belly up in Hanoi lake, one year after similar mass death

Locals started noticing some dead fish on the Hoang Cau Lake in Dong Da District at around 2 a.m. on Thursday. More floated belly up after that and it's etimated that tons of fish had died by Friday morning.

Most of the dead fish are barbs and carps. Some are as big as 10 kilograms.

Sanitation workers spend the whole night picking up the dead fish.

Tests found a slight drop of oxygen level in the water. No conclusion has been made about the cause.

Bags of dead fish pile up by the lake.

Workers bring a fish to the garbage truck.

A similar mass fish death happened in early June last year when dozens of tons of dead fish were collected from the lake. Officials then blamed sudden change of weather and pollution. The lake is connected to a stormwater drain system, but sewage does not go here.