The Ocean Park Conservation Foundation on Thursday said it had retrieved the carcasses of two dolphins from Pui O Beach on Lantau, to try to find out why they died.

The foundation said one of the dolphins was a newborn, while the other was a severely decomposed adult of 2.4 metres in length.

The foundation urged people to report any stranded dolphins or whales to the 1823 government hotline.

It also called on people not to use shampoos or body washes while on boats, to prevent ocean pollution.

The foundation’s Assistant Scientific Manager, Dr Edgar Leung, estimated that the two Chinese white dolphins died over a week ago. He added that based on past experience, it will be almost impossible to find out the cause of their deaths.

“Since 2006… we have investigated over 600 cetacean stranding cases altogether. However, most of the carcasses were found severely decomposed, like these two cases. Therefore, the cause of death is hard to determine. Only 10 percent of them can be addressed,” he told RTHK.

Leung said possible causes of death include entanglement in fish nets or a bacterial infection. He said a necropsy will be carried out.

The chairman of the Dolphin Conservation Society, Taison Chang, also said it will be very difficult to determine the cause of the deaths.

"Because mainly of the condition of the decomposed body. Most of the time, dead bodies recovered are very decomposed. So even if there is like a cut by a fishing line or a cut by propellers of a boat, the decomposed part, the body tissue, can easily mask the injury," he said.