Hong Kong authorities are scrambling to find out why nine monkeys – three of them endangered – died in a span of just two days at the city’s oldest zoo. Part of the zoo has been sealed off to be disinfected.

Hong Kong’s oldest zoo sealed off part of its grounds on Tuesday as it brought in experts to seek answers for the death of nine monkeys in just two days.

Three of the nine monkeys were of endangered species.

Authorities of the Hong Kong Zoological and Botanical Gardens are now keeping a close watch on a monkey which is displaying unusual movement and appetite.

The sealed parts of the zoo are being cleaned and disinfected.