Officers will today return to St Osyth to search the areas where a lion may have been spotted.
The big cat was seen in fields off Earls Hall Drive (pictured is the entrance to Earls Hall Drive) in the village just before 7pm yesterday.
Residents were told to stay indoors as search teams worked throughout the night to track down the large cat, which was spotted in a field by a member of the public last night.
Essex Police has enlisted the help of experts from Colchester Zoo who believe
the sighting to be genuine after viewing a photograph of the animal taken by a local.
Two police helicopters using heat-seeking equipment have been involved in the hunt for the animal, while zoo workers said to be armed with tranquilliser guns have also joined armed officers.
Police immediately issued a warning to residents to stay inside their homes as officers began a search near where the animal was spotted.
Che Kevlin said he heard what he believed to be a roar whilst out walking his dog last night.
"I heard a loud roar at 10pm. It sounded like a lion," he told the BBC.
"It was worrying as we had just been for a walk with the dog. We saw the police helicopter but thought it was just searching for a person.
"It sounded like the roar of a lion. We have a field and wood just behind our fence, so you never know."
Police are trying to establish where the lion may have come from and have urged anyone who sees it to call 999.
A force spokeswoman confirmed the animal had not escaped from Colchester Zoo, as all its animals had been accounted for
There have been rumours that the big cat may have escaped from a circus that had been performing in the Essex area, but they are yet to be substantiated.
The Great British Circus was based at Clacton Airfield but its run in the area ended around a fortnight ago, according to a local events website.
The police spokeswoman added: "We are investigating where the lion may have came from but it is fairly safe to say that it did not escape from Colchester Zoo."
Pub landlord Dave Sparks, who runs the Red Lion pub in St Osyth, described the police hunt as "surreal".
He told ITV News: "You don't really expect to be told there's a lion wandering around the area.
"No one really felt there was any immediate danger in the village - a couple of families with young children were a bit worried but after a while they were ok."
An Essex Police spokesman said officers would return to areas where the animal had been spotted during daylight hours to look for signs it had been there,
such as pawprints.
Anyone who sees the lion is advised to call 999.