Melioidosis, a bacterial infection, was responsible for killing at least nine monkeys at a Hong Kong zoo, authorities said, as a further two died over the weekend, taking the total to 11 in the past week.

Eleven monkeys have died over the past week, with a further two dying over the weekend. Authorities say the bacterial infection melioidosis killed at least nine of the monkeys at Hong Kong's oldest zoo.

Melioidosis cases witness a spike after heavy rainfall, hurricanes or other severe weather events as it leads to the rise of bacteria on the surface of the soil, according to the Centers for Disease Control and Prevention.

The death of nine monkeys over two days at a zoo in Hong Kong is believed to have been caused by a bacterial infection, the city’s authorities said. The death toll rose to 11 over the weekend after two more monkeys died.

A 11th monkey from the Hong Kong Zoological and Botanical Gardens was found dead on Sunday whilst under quarantine, the government has said. In a statement issued on Sunday evening, the government said a common squirrel monkey died while being placed under isolated surveillance.

Common squirrel monkey was one of two that was put under isolated surveillance last week after showing signs of illness.