The escape and eventual recapture of a gorilla at London Zoo “could have ended very differently” and should be subject to an inquiry, a charity has said.
The Born Free Foundation said the incident was a “startling reminder” of how dangerous wild animals could be when kept in captivity.
The zoo was put in lockdown on Thursday after a male gorilla escaped from its enclosure and had to be tranquilised.
Born Free said the Zoos Expert Committee, a Government advisory body, should investigate the safety and welfare of great apes in UK zoos.
Chris Draper, associate director at the foundation, said: “While we are relieved that this incident apparently ended without injury to visitors or to the gorilla, it is yet another startling reminder of the risks associated with maintaining dangerous wild animals in captivity.
“This incident could have ended very differently. We are calling for an urgent inquiry into the circumstances surrounding this escape, and into safety procedures at London Zoo.”
Armed police had to be called to the attraction as visitors were evacuated while keepers dealt with the emergency.
Some reported being locked inside buildings at the zoo, which is one of London’s top tourist spots.
The 18-year-old western lowland gorilla, named Kumbuka, was eventually subdued by vets and returned to his den.
In a statement, the zoo said Kumbuka “got out of his den at ZSL London Zoo and into a non-public zoo keeper area at 5.13pm.
“The gorilla remained contained within the exhibit off-show area. Staff responded immediately and (he) was tranquilised by vets.
“We can confirm he is awake and well.”
Malcolm Fitzpatrick, curator of mammals at the zoo, described Kumbuka’s escape as a “minor incident” and said visitors were “never in any danger”.
The incident is now under investigation, he said.
It is not yet clear how Kumbuka got free.
Visitors to the gorilla attraction reported seeing the “lead male” apparently agitated and charging at the enclosure’s glass walls moments before the escape.
One visitor, Rob Hogan, told Sky News he saw a “big male” gorilla throw himself at a window moments after he and other people took pictures of the animals in their enclosure.
Mr Hogan said the glass shook and the creature made a “loud boom” noise, adding his heart was racing.
The gorilla – almost certainly Kumbuka – then sat down, clasped his hands and “all seemed calm”.
Shortly after, Mr Hogan and his group left and headed towards the reptile house where they were asked to remain by staff as they were “running a drill”.
They were allowed out about 20 minutes later.
According to the zoo’s website, there are seven gorillas living in Gorilla Kingdom, which was opened in 2007 by the Duke of Edinburgh.
In May, a gorilla at Cincinnati Zoo in the US was shot dead by keepers after it grabbed a four-year-old boy who had fallen into a moat.
Harambe, a 17-year-old male western lowland, was killed after he dragged the youngster around for 10 minutes.