Indonesian authorities have arrested two men on suspicion of poaching Sumatran tigers and seized a skin and bones taken from one of the rare animals, a national park official said Monday.

Awaludin and Sabian, who like many Indonesians go by one name, were detained Saturday by police and forest rangers in a village in North Bengkulu district on western Sumatra island.

Authorities acted on a tip-off from villagers who said the men often hunted for protected species in the enormous Kerinci Seblat national park, believed to be home to some 150 Sumatran tigers.

The International Union for Conservation of Nature classifies the Sumatran tiger as critically endangered and estimates as few as 440 remain in the wild.

“We tailed the men all day after being tipped off and arrested them late Saturday,” national park chief Arief Tongkagie told foreign media agencies.

“They were carrying a preserved tiger skin and its bones.”

The men, in their 40s, are still being questioned by police. They could face up to five years in jail if found guilty of breaking Indonesian laws that protect endangered animals.

Police are also investigating whether they were part of a larger wildlife poaching syndicate.

Poaching is a major cause of the rapid decline of Sumatran tiger populations. The creature’s body parts are used in traditional Asian medicine and fetch a high price on the black market.

Apart from being hunted, the animals are also under threat from the destruction of their rainforest habitat to make way for palm oil and paper plantations.

The Sumatran tiger is the smallest of the tiger species and is distinguished by thick black stripes on its orange coat.