Nearly 1,000 people from different forces and agencies have been mobilised to clean the West Lake following the death of up to 200 tonnes of fish.

By yesterday afternoon West Lake had almost appeared to have returned to normal as only a small amount of dead fish were found.

Dozens of aeration devices have been installed to provide oxygen to save fish in the lake. 

Around 1,000 people from Hanoi's wards and military forces jointly collected the dead fish and attempted to treat the water.  

Nearly 30 motorboats with hundreds of soldiers have trailed the lake looking for dead fish. 

Environmental workers are ready to transport the dead fish. 

A preliminary report from the Hanoi People’s Committee indicated that the extraordinarily high ammonium and oxygen depletion were partially responsible for the mass death fish in the West Lake.

Prime Minister Nguyen Xuan Phuc has urged Hanoi authorities to find out the cause of the incident.