JAKARTA, Indonesia?One of the world's largest paper companies plans to clear a large swath of unprotected forest in Indonesia being used as a sanctuary for critically endangered orangutans, according to environmental groups working in the area.

Singapore-based Asia Pulp & Paper and a local joint venture partner, Sinar Mas Group, have received a license to clear hundreds of hectares (acres) of trees just outside the Bukit Tigapuluh National Park on Sumatra island, WWF-Indonesia and four other groups said Tuesday.

Though not protected, the plush, lowland forests are considered an important area for biodiversity and have been used since 2002 as a release point for around 100 Sumatran rehabilitated orangutans?some orphaned when their mothers were allegedly killed by workers on nearby palm oil plantations.

"It took scientists decades to discover how to successfully reintroduce critically endangered orangutans from captivity into the wild," said Peter Pratje of the Frankfurt Zoological Society. "It could take APP just months to destroy an important part of their new habitat."

Asia Pulp & Paper could not immediately be reached for comment.

But the company said in a statement released last month that the government had officially allocated the forest for plantation use and that it would follow all legal procedures?including carrying out an independent, third party assessment about potential conservation threats.

There are an estimated 50,000 to 60,000 orangutans left in the wild, around 10 percent of them on Sumatra, and the rest on the nearby island of Borneo, which is divided largely between Indonesia and Malaysia.

Rain forests have been cleared and burned at alarming rates on both islands to make way for lucrative palm oil plantations and for timber.

The forests around Bukit Tigapuluh National Park are also home to 100 of the last 400 critically endangered Sumatran tigers left in the wild, said Dolly Priatna of Zoological Society of London, and roughly 50 endangered elephants.

The groups protesting the APP's plans?which include WARSI and the Sumatran Tiger Conservation and Protection Foundation?have written an official letter of complaint to the government.