Story highlights Footage of armed police walking through zoo posted on social media

Reports that the public has been locked inside buildings for protection

(CNN) A London Zoo silverback gorilla briefly escaped his enclosure Thursday but did not make it to any public areas, officials said.

Metropolitan Police received a call just after 5 p.m. asking for assistance, police told CNN. Kumbuka, 18, was contained to the exhibit's off-show area used by zookeepers.

The western lowland gorilla was subdued by a tranquilizer dart and returned to his den. "We can confirm he is awake and well," the zoo said in a statement.

Gorilla update, animal control officers have arrived, still locked in gift shop! #WWWF16 pic.twitter.com/gnPa20eByR — Leftfield Research (@LeftfieldSE1) October 13, 2016

Footage posted on social media showed armed officers walking the grounds.

Other members of the public reported huddling inside zoo buildings for protection. Officials said they were not certain how Kumbuka -- who has been at the facility since early 2013 -- made his escape.

Read More