HONG KONG, Oct 15 — Zoo authorities in Hong Kong are keeping close watch on a monkey that is behaving unusually a day after the ninth death this week of one of the animals, while hastening tests to find out what killed them.

During the monitoring, the city’s Zoological and Botanical Gardens (HKZBG) will keep shut its mammals section, after having closed it for disinfection and cleaning yesterday.

"Government departments will speed up autopsy and toxicological testing,” the government said in a statement, as they scramble to pinpoint the cause of the deaths.

The ninth monkey, belonging to the white-faced saki species, died a day after Sunday’s deaths of a De Brazza’s monkey, a common squirrel monkey, three cotton-top tamarins and three white-faced sakis, it added.

Authorities will also keep watching the status of a De Brazza’s monkey that has displayed unusual movement response and appetite since yesterday, it said.

Built in 1860, the territory’s oldest park houses about 158 birds, 80 mammals and 21 reptiles in roughly 40 enclosures.

"The health conditions of all 80 animals in the HKZBG are normal,” the government said, while officials held an urgent meeting today.

Animal welfare group People for the Ethical Treatment of Animals (Peta) said the incident raised concerns about the risks of outbreaks of diseases such as monkeypox that can jump to humans from animals. — Reuters