Asia Pulp & Paper (APP) is set to clear a large area of unprotected forest in Indonesia being used as a sanctuary for critically endangered orangutans, according to environmental groups working in the area.

APP has received a license to clear hundreds of acres of trees just outside the Bukit Tigapuluh National Park on Sumatra island, WWF-Indonesia and four other groups said.

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.