Visitors were evacuated from Chester Zoo when a large fire broke out in one of its attractions.
The zoo tweeted the blaze was in its Monsoon Forest habitat.
One person was treated for the effects of smoke inhalation but there were no other reports of injuries. Fifteen fire crews have been tackling the blaze.
In a statement, the zoo said: "Sumatran orangutans and other mammals are all accounted for. We are working hard to account for all other species."
Police said the fire was reported just before 11:30 GMT.
Some zoo visitors tweeted images from the scene including Sophie Flynn, who said staff were "working hard to deal" with the fire, which "happened very quickly".
"It started as a little fire... which we saw but it's obviously much worse now!"
David Clough, who lives across the road from the zoo, said: "We first saw signs of the fire shortly after 11.30 GMT."
He added: "It was spreading across the roof in strong winds for a while.
"Lots of fire engines arrived quickly.
"We were very worried for the people and animals that would have been in the building."
The zoo tweeted to say it had closed the whole site, adding: "Visitors have been evacuated and our response team is working alongside emergency services to bring the situation under control."
At the scene: Gerry Jackson, BBC News
Flames were fanned by today's very strong winds and raced across the roof of the Monsoon Forest enclosure.
As hundreds of visitors were being evacuated from the wider premises, zoo staff were leading threatened animals to safety.
The zoo has closed and we have no indication of when it will reopen.
Of course an investigation has begun into the cause of the fire.
Even though visitor numbers would have been much lower on a day of bad weather like today, this is obviously a very dramatic event for one of northern England's premier attractions.
The Monsoon Forest habitat is the UK's largest zoological building, according to the attraction, and opened as part of the zoo's islands section in August 2015.
The 14-acre section houses Sumatran orangutans, rhinoceros hornbills, crocodiles and a variety of plant species.
It has its own tropical weather conditions, with temperatures reaching 26.6C to replicate conditions in South East Asia.
It has more than 21,000 animals of 500 different species and has been the subject of many TV programmes including the BBC's Our Zoo drama in 2014.
The venue says it plays a significant part in wildlife conservation, helping to save endangered species.