After the thunderstorm in Hanoi of a series of prolonged hot days, fish at the CV1 Park regulating lake (Cau Giay ward, Hanoi) floated and died sporadically from May 30. On May 31, the amount of dead fish drifting ashore increased sharply, forcing functional forces to urgently deploy collection and treatment work.
In the afternoon of May 31, reporters' records at the scene showed that on-duty forces were urgently collecting dead fish and garbage around the lake area. According to initial records, the sudden change in weather after a long period of hot weather may cause fish to suffer heat shock and die en masse.

Drifting fish carcasses, forming large patches along the stone embankment, begin to decompose and emit a fishy odor, affecting the environment and daily life of people coming to play and exercise in the park.
To accelerate the progress of cleaning the lake, Cau Giay Ward People's Committee coordinated with Hanoi Drainage One Member Limited Company to mobilize dozens of workers, youth union members and specialized vehicles to participate in collecting and transporting dead fish.
Under the lake, workers use boats and specialized rackets to pick up dead floating fish and bring them ashore for treatment. In the embankment area, forces collect garbage, scoop dead fish into sacks to transport them away from the scene.
In order to limit wastewater and odor from spreading to the walking area, the dead fish after collection are loaded onto specialized vehicles and transported immediately to the gathering place for treatment according to regulations.

In parallel with the collection work, functional forces conduct environmental sanitation, spray disinfection and wash the walking path area around the lake. The synchronous treatment aims to limit environmental pollution, ensure landscape and living space for people.
Talking to reporters, a representative of Cau Giay Ward People's Committee said that by the end of May 31, most of the dead fish drifting ashore had been collected and treated, helping to significantly reduce the stench around the lake area. However, in the face of complicated weather developments, the locality and management unit continue to maintain forces to monitor and be on duty to promptly handle if more fish deaths arise.