Authorities say a bacterial infection has killed at least nine monkeys at Hong Kong's oldest zoo, as a further two died over the weekend.

A total of 11 monkeys have died in the past week. 

Part of the zoo, which was built in 1860, has been shut since authorities reported the first batch of monkey deaths on October 14. 

The deceased monkeys included the De Brazza species as well as one common squirrel monkey, cotton-top tamarins and white-faced sakis.

Authorities said nine monkeys died of sepsis after catching the infection melioidosis.

They said autopsies found a large amount of the melioidosis-inducing bacteria in the monkeys organs, which likely came from soil near the monkeys habitat.

Further tests are needed to determine the cause of death of the latest two monkeys.

Hong Kong's culture and tourism minister, Kevin Yeung, said works at the zoo required digging up the soil near where the monkeys lived.

He said workers were then believed to have brought contaminated soil into the cage through their shoes.

"We have cordoned off the whole mammals section for the time being, so there will be no sort of contact between normal citizens with the animals," he told local broadcaster RTHK.

The bacteria is particularly common in moist clay soil. 

Authorities have advised it can affect both people and animals, but it is unlikely to be passed to humans.

The zoo houses about 158 birds, 70 mammals and 21 reptiles in about 40 enclosures.

Reuters