Endangered species conservation scientists from the NGO Conservation International (CI) have announced the resumption of their mission in the Veun Sai-Siem Pang National Park in Ratanakkiri and Stung Treng provinces after having made a series of discoveries since 2007 of nearly 400 groups of yellow-cheeked crested gibbons (Nomascus gabriellae) with 1,500 or more of the primates in each of them.