The mass fish deaths happened in the lake area which runs along Nhat Chieu Street in Quang An Ward over the past two days. 

On the evening of September 13, workers tried to gather the dead fish and then put them into around 100 bags. Until the early morning of the next day, the work was finished. 

Most of the fish is tilapia and barb weighing around 500 grammes. 

According to workers, they collected around two tonnes, while there was still a large amount of remaining dead fish left in the lake. 

In July this year, around 500 environment workers and volunteers jointly gathered around 25 tonnes of dead fish in the lake. Director of the Hanoi Department of Construction Le Van Duc said that the phenomenon would be due to the heat earlier.

In October 2016, hundreds of tonnes of fish were also found dead on the West Lake. Test results from the Hanoi Department of Natural Resources and Environment showed that the fish died from lack of oxygen.