JAKARTA (Reuters) - A Bornean orangutan, a critically endangered species, has been found stabbed to death in Indonesia’s Central Kalimantan province, a conservation official said on Tuesday.

Authorities said the case was the latest in a string of “unnatural deaths” of orangutans on the island, to which they are native.

The great ape was found floating in a river and had been dead for at least two days, said Adib Gunawan, head of the Natural Resources Conservation Agency in central Kalimantan.

“We found that it was stabbed multiple times using a sharp tool,” Gunawan told Reuters. “We are still investigating the case.”

The World Wildlife Fund estimates there are 104,700 Bornean orangutans, known for their broad faces and dark brown fur, left in the world.

Last year, two orangutans that had been killed were discovered in East Kalimantan, media have said.

Indonesia has vast swathes of plantations growing palm oil or coffee on deforested land that conservations say often encroach on or disrupt ecosystems. Plantation workers sometimes encounter wildlife and may capture or kill the animals.