A national veterinary lab said Friday that two hyenas at the Denver Zoo in the US state of Colorado tested positive with Covid-19, the first verified instances among the animals globally (local time).

According to the National Veterinary Services Laboratories, samples from a range of animals at the zoo, including spotted hyenas, were tested after several lions at the facility became unwell.

The hyena samples came back presumptively positive at a Colorado State University lab, and the instances were confirmed by the national lab.

In addition to the two hyenas, 11 lions and two tigers at the zoo tested positive for the virus.