HONG KONG — Zoo authorities in Hong Kong are keeping a 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 on Monday.

“Government departments will speed up autopsy and toxicological testing,” the government said in…