The Leisure and Cultural Services Department announced on September 15 that the Environmental Protection Department had classified the water quality at Trio Beach in Sai Kung District as Grade 4, according to a government notice issued that day. That grade means the beach was not suitable for swimming, and a red flag was hoisted there.

Beachgoers were advised not to swim at the beach until further notice. The notice did not say how long the restriction would remain in place or what had affected the water quality.

The grading and the red flag reflect conditions reported on September 15; the notice gives no later update on water quality at the beach.