London Zoo went into lockdown on Thursday afternoon following an incident involving a gorilla that escaped from its enclosure and was subdued with a tranquilizer dart.
Staff at the zoo in central London were sent a message informing them an "animal emergency incident" was underway while the site was secured and members of the public filmed armed police officers outside.
An email sent to London Zoo staff at 5.15pm warned them to stay inside: "An animal emergency incident is currently being managed on the London Zoo site. All staff are instructed to remain within buildings and not to venture out until the all clear has been given.
"If any member of your team is away from their desk and in the zoo grounds, please make every effort to contact them via DECT or mobile phone and alert them to the emergency. Thank you for your co-operation."
A follow-up email to staff confirmed that the incident had been contained:
Our male gorilla, Kumbuka, got out of his den and into a non-public keeper area at 5.13pm. The gorilla remained contained within the exhibit’s off-show area at all times and there was no injury to anybody.
Our staff responded immediately and he was tranquilized by vets and returned to his den, where he was awake and well within two hours.
The exhibit was secured immediately and we are grateful to all of our staff and visitors for their co-operation, enabling us to resolve the situation quickly and efficiently.
A full investigation will be carried out to determine what happened.
Evening events continued at the zoo as normal, and keepers will monitor the gorillas but we expect Gorilla Kingdom to be open as usual tomorrow.
"He's a fucking psycho, that ape," a zoo source said of Kambuka. "He's smashed the enclosure glass a couple of times."
Tweets from members of the public suggested the gorilla threw itself at the glass of its enclosure, although the London Zoo source said this wasn't the case and that there was no immediate risk to the public.