HONG KONG (AP) — Nine monkeys who died in Hong Kong’s oldest zoo in two days this week had been infected with an endemic disease, possibly after some digging work near their cages, officials said on Friday.

Secretary for Culture, Sports and Tourism Kevin Yeung said in a press briefing that the animals in the Hong Kong Zoological and Botanical Gardens contracted melioidosis and the disease later caused them to develop sepsis.

Yeung stressed that such infections typically occur through contact with contaminated soil and water and that there is generally no danger to humans from contact with infected animals or people.