Five wolves managed to escape from Colchester Zoo after the perimeter fence was damaged.
Two of the wolves were shot and killed, one was recaptured while the other returned voluntarily.
Essex Police are searching for the remaining wolf who is thought to be sheltering in thick undergrowth.
A police helicopter has been deployed to assist with the search.
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Police are hunting for a wolf after it escaped from Colchester Zoo earlier today.
The animal was reported missing at around 8am
Essex police said a helicopter had been dispatched to assist with the search, but insisted the wolf "does not pose a risk to the public".
"Police are currently assisting staff at Colchester Zoo searching for a wolf that's escaped from the zoo site," a police spokesman said.
"Officials at the zoo have said that wolves are naturally timid, and provided they're not cornered in any way, do not pose a risk to the public."
Colchester Hospital University NHS Foundation Trust has been placed in special measures by health sector regulator Monitor.
Unison has called for a "full and thorough investigation" into claims of "harassment and bullying" at Colchester Hospital University NHS Foundation Trust.
Our members took a brave step by reporting to the CQC that they were being bullied and harassed by senior managers to falsify records relating to cancer patients.
They raised their concerns repeatedly and in emails to senior managers, right up to the chief executive, but they were ignored.
A hospital trust has been reported to the police after staff said they were being "bullied" to falsify data relating to cancer patients.Read the full story ›
A patient was referred to Colchester Hospital University NHS Foundation Trust's cancer service in May last year.
In the records book, the referral had been documented that the patient turned up in July, two months later.
That made it look as if the hospital were meeting the national guideline of treating patients within 62 days.
Is this serious? Well, every expert we've spoken to has revealed the big issue with cancer is that time is everything.
With every delay in treatment, the cancer can grow, can spread and could prove fatal.
We don't know that's happened at Colchester but we do know staff have been bullied into changing the records and taking risks with peoples' lives - just to make it look as though they are meeting a national requirement, when in fact they are not.
The Department of Health (DH) has admitted poor patient care and hospital cover-ups have gone on for "too long" and the Department said a new system will identify failings in the NHS.
It comes after a health watchdog found that 22 cancer patients at Colchester Hospital University NHS Foundation Trust may have missed vital treatment after staff complained they were pressurised into changing waiting time data to meet national targets.
Reacting to the findings, the DH said: “For too long, patients have had to put up with poor care and cover-ups because it was too inconvenient to expose and take action.
“That’s why we’ve strengthened the inspection regime, given whistle-blowers extra protection and made it a duty for staff to raise concerns."
It added: “What’s happened at Colchester shows the new system working; the spotlight shone on failings and extra support being given to quickly improve standards.”
We have been working on a series on cancer care in the UK for three weeks and everyone we have spoken to stresses how important early diagnosis and early treatment is.
Delaying treatment for even a few days, the cancer can grow, and it can spread and it becomes much more dangerous.
To find, in this case, the allegation was that staff were bullied into changing records so it made it look as if patients were getting timely treatment when in fact they were not, I think this is one of the most shocking things I have heard, in a long time.
On behalf of the trust, I apologise to the patients, relatives and carers who we have let down. We are very sorry for the worry, distress and concerns that have been raised by the publication of the CQC report into our cancer services.
Our priority is to focus on the safety and welfare of all cancer patients.
We are learning from this inspection, we are changing the way we do things where necessary and we are doing this quickly so that we are certain that all cancer patients using our hospitals receive the best possible care.
It is also extremely disheartening for us to learn that it appears from the CQC inspection report that some inappropriate changes were made to cancer waiting time data."
A report by the Care Quality Commission (CQC) has found a number of cancer patients suffered "undue delays" at Colchester Hospital University NHS Foundation Trust.
A spokesman said that of the 61 care records examined, 22 showed that people had been "placed at risk of receiving care that was unsafe or not effective, due to delays in receiving appointments or treatment".
The CQC said that the trust has written to 30 patients, or their next of kin - where patients have died, offering to review their treatment.
The Chief Inspector of Hospitals Sir Mike Richards said "It is shocking to think that people's lives may have been put at risk for the sake of the waiting time figures".
He has recommended that the hospital should be put into special measures