Housed in five separate cages, the deceased monkeys included the De Brazza species as well as one common squirrel monkey, cotton-top tamarins and white-faced sakis.
The zoo, located just above the city's financial centre, has shut its mammals section since Oct. 14, when authorities reported the first batch of monkey deaths.
The government said it would continue to close the section and provide protective gear and health monitoring for staff taking care of the animals.
"The health conditions of the 78 mammals are normal," the Leisure and Cultural Services Department said.
Authorities said 11 monkeys died of sepsis after catching melioidosis. Tests were being done on the 12th deceased monkey to find out the cause of death.
Autopsies in the past week found a large amount of the melioidosis-inducing bacteria in the monkeys organs, which likely came from soil near the monkeys habitat, authorities said.
The zoo, built in 1860, is the oldest park in Hong Kong.
