A dead porpoise, suspected to have been carrying a stillborn calf, was discovered in Hong Kong waters on Tuesday.

The mammal was spotted by boat captain Vincent Tong Chi-kin in the waters near Ap Chau, one of the city’s outlying islands, on Tuesday morning. His vessel was conducting coastal clean-up work for the Food and Environmental Hygiene Department.

“We spotted a grey-black object when steering from Lai Chi Wo to Ap Chau. It turned out to be the body of a mammal when we got close,” he said.

He added that the six-foot (1.8 metres) carcass was intact, with no visible scratches.

“A closer look, I suspected there was a calf under its abdomen, as I saw a small fin from it,” he said.

Tong reported the case to the Agriculture, Fisheries and Conservation Department immediately, and later saw marine police searching for the mammal about an hour afterwards.