The provincial livestock office in Chiang Mai said in a statement on Friday that testing detected the highly infectious canine distemper virus as well as bacteria affecting the respiratory system.

“When tigers fall ill, it is more difficult to detect than in animals like cats or dogs. By the time we realised they were sick, it was already too late,” Somchuan Ratanamungklanon, director of the national livestock department, told local media.

The park where the deaths occurred, Tiger Kingdom, could not be reached for comment on Saturday.

Its website advertises a chance for visitors to touch and take photos with the big cats.

“These tigers died the way they lived – in misery, confinement and fear,” animal rights organisation PETA Asia told AFP.

“If tourists stayed away, these places would quickly become unprofitable, and tragedies like this would be far less likely to happen,” the group added.