Visitors have been evacuated from Hamerton Zoo as police and air ambulance were spotted outside the attraction.
People took to social media to tweet about the closure in Huntingdon, Cambridgeshire.
Chris Hubbard posted: “Police and air ambulance called to @HamertonZoo and guests are being cleared out. Hope everyone’s okay.”
He also tweeted a picture of the scene which appeared to show an air ambulance and emergency services on the scene.
Cambridgeshire Police tweeted they had attended an incident at the zoo but confirmed no animals had escaped.
In a statement on Facebook the force added: “We were called at around 11.15am to reports of a serious incident at Hamerton Zoo Park, Steeple Gidding.
“Officers attended the scene along with ambulance crews and Magpas (air ambulance).
“We are unable (to give) further information available at this time, however, we can confirm that no animals have escaped and members of the public are safe.
“We will provide a further update when we are able to.”