A fire broke out at London Zoo early on Saturday morning, engulfing a cafe and shop near an animal petting area, and leaving one aardvark missing.
Several staff were treated for smoke inhalation and shock following the blaze, which broke out in the Animal Adventure section shortly after 6:00 am (0600 GMT), the zoo said.
"Duty staff that live on site at the zoo were on the scene immediately, and started moving animals to safety," it said in a statement.
"The London Fire Brigade were on the scene within minutes and the fire was brought under control by 9:16 am.
"A number of zoo staff have been treated at the scene for smoke inhalation and shock. Our staff are now in the process of assessing the situation in difficult conditions.
"At present one aardvark is currently unaccounted for."
The zoo, in Regent's Park not far from the popular Camden Market, said it would remain closed "until further notice", adding that investigations were underway to establish the cause of the fire.
It took more than 70 firefighters more than three hours to bring the fire under control, the London Fire Brigade said.
Fire officer Clive Robinson said: "The fire mainly affected the cafe and shop. Part of nearby animal petting area was also affected.
"Firefighters worked hard to bring the fire under control as quickly as possible and to stop it from spreading to neighbouring animal enclosures.
"Crews will remain at the scene throughout the morning damping down any remaining pockets of fire."
The zoo opened in 1828 and is now a leading conservation organisation as well as a major tourist attraction.