Chester Zoo was evacuated after a fire broke out in the Monsoon Forest habitat area.
The popular tourist attraction was closed as fire crews attempted to bring the blaze under control on Saturday.
The zoo's animal teams worked to move all animals away from the incident, and the fire brigade later confirmed all animals were accounted for.
One person was treated for smoke inhalation, an ambulance spokeswoman confirmed.
In a statement on its Facebook page at 12.15pm on Saturday, the zoo said: “We can confirm that the fire brigade is currently fighting a fire inside our Monsoon Forest habitat.
“Visitors have been evacuated and the zoo’s response team is working alongside emergency services to bring the situation under control.
“The zoo is now closed. We will update you with more details as soon as we have them.”
"Visitors have been evacuated & our response team is working alongside emergency services to bring the situation under control," the zoo's official Twitter account added.
A spokeswoman for North West Ambulance Service said it was called to the scene at 11.42am.
"We had two rapid response vehicles and one ambulance on the scene, all of which cleared as there were no patients," she said.
"There is one patient with smoke inhalation. We've got an officer on the scene."
Chester zoo is home to about 21,000 animals, including some of the world's most endangered species.
The attraction’s Monsoon Forest habitat is described as “the largest indoor zoo exhibit in UK history”.
One eyewitness, David Clough, said high winds fanned the flames in the inflatable roof of the building, adding: "We were very worried for the people and animals that would have been in the building."
The 50 year old, who lives across the road from the zoo, said: "We first saw signs of the fire shortly after 11.30am.
“The Monsoon Forest building in the zoo’s new Islands development was on fire.
“It has an inflatable roof that was burning. Lots of flames and smoke.”
He added: “Orangutans and gibbons are our nearest neighbours there, but there are many other animals, including free-flying birds.
“It was spreading across the roof in strong winds for a while.
“Lots of fire engines arrived quickly.
“By about 30 minutes ago the main flames had gone, but there’s a smaller fire still burning at the southern end of the roof.”
A zoo visitor, who did not want to be named, said: “We were in the Monsoon enclosure when it happened and were rushed out due to an electrical fire. It spread very quickly.
“The staff ensured all the members of the public were safe. Many staff (were) running towards the fire, (I’m) assuming to help with evacuating animals.
“The entire zoo is closed – a shame as we've travelled up from Plymouth.”
An aardvark and four meerkats were killed at London Zoo almost a year ago after a fire broke out on 23 December.
It took 70 firefighters to tackle the blaze, which left nine people injured.
The cause of the fire is still unknown.
Press Association contributed to this report
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