Visitors were rushed to safety after the ape vanished from its enclosure.
Twycross Zoo staff ushered visitors inside at the Leicestershire Zoo yesterday.
The panic lasted around 15 minutes before the animal was recaptured, reports Birmingham Live.
One witness spoke of the panic that ensued after it escaped at around 2.20pm yesterday.
She said: “People were running and keepers were ushering people into sheds and rooms and holding the doors closed.
“Staff weren’t saying anything really, but did keep everyone locked in and safe”
“They locked everyone in the soft play building too.
“There were lots of crying children and frantic parents.
“Someone in our section had a panic attack.
“Staff weren’t saying anything really, but did keep everyone locked in and safe.”
Another witness, who called for an investigation, said: “How on earth it escaped, I will never know.
“This should never have happened.”
And a fellow visitor, Rhiannon Clapperton, said: “All of the staff looking after us in the cafe area by gibbons were fab.”
Karen Clarke, the zoo’s chief operating officer, said yesterday: “We would like to thank our visitors for their patience during a brief interruption to their day out this afternoon when Storm, one of our gibbons, accidentally over swung onto an area on the edge of his habitat.
“Our professional animal team worked together to corner off the area in order to allow him a safe route back into his home where he quickly returned.”