A wolf escaped after strong winds blew down a fence at a sanctuary near a school, witnesses said.
Police have told school children not to go outside and members of the public not to approach the animal which is on the loose from the UK Wolf Conversation Trust sanctuary in Beenham, near Reading.
Officers were called at 8am on Thursday to the scene near the centre in Picklepythe Lane - which is just over three miles from the Duchess of Cambridge's family home in Bucklebury.
Tony Roe, who lives near the wolf sanctuary, first learned of the escape when taking his son to Beenham Primary School at about 8.25am.
The 53-year-old, who runs Theale-based Tony Roe Solicitors, said: "We got to the school gate and a police officer was standing outside. I asked if something was happening and she said a fence had blown down at the sanctuary and a wolf had escaped.
"She was making sure the children got into school safely and the gate was secure.
"About five minutes later I saw a police car with blue flashing lights heading towards the sanctuary.
"It was very windy - about 30 or 40 mph. It woke me up in the night.
"Presumably the sanctuary has protocols about what to do in this situation. It's great the police were there so quickly.
"I've spoken to other parents and obviously everyone wanted to make sure the children are safe but no-one is concerned.
"We hope the wolf is captured safely."
Founded in 1995, the sanctuary currently has ten wolves from the Artic and Northwestern breeds, living in four packs. Two of the packs are from Dartmoor and another from Quebec. The remaining wolves were born at the sanctuary.
Mr Roe, whose property neighbours the sanctuary but is separated by several fields, said the wolves are much loved in the village.
He said: "The school's emblem is a wolf and there is a lot of support here for what they do.
"We have seen them being walked on leads in the woodland."
A spokeswoman for Beenham Primary School said it was on lockdown to stop anyone from going outside until they were advised otherwise by the police, adding: "We are all fine, we all know the wolves and no-one is worried."
A Thames Valley Police spokesman said: "Officers have sight of the wolf and are working with staff from the sanctuary to detain it."
But the force would not confirm how the wolf escaped. The sanctuary has so far declined to comment.
Sian Champkin, whose husband works at Elstree Independent Boys Preparatory School in nearby Woolhampton, said pupils have also been told not to go outside.
The 37-year-old said: "He phoned me to tell me about it because we have a child, a dog and a cat and not to go outside. The sanctuary is about a mile away as the crow flies. I was slightly shocked, nothing like this has ever happened before."
Elstree School refused to comment.