Officials at the Apenheul primate park in Apeldoorn are investigating how a nine-year-old orangutan came to drown in the water surrounding the island where she lived.

The primate, named Merah, was born in the zoo and had a cautious nature, officials say.

One visitor has since said he saw Merah jump into the water, behaviour which officials say is extremely unusual. Orangutans are careful around water because they cannot swim.

Zoo staff will now examine camera footage to see if they can find out what happened. Merah’s body will also undergo a post mortem to see if there are any clues.