A fire broke out in the tropical house at Cologne Zoo on Tuesday evening.
Local residents reported smoke over the zoo around 6:20 p.m., said a spokeswoman for the fire brigade.
Food was probably on fire.
More than 50 emergency services are on site.
Several media reported online.
A spokesman for the zoo initially declined to comment on the fire.
"The extinguishing work is progressing," said the fire department spokeswoman about an hour after the alarm.
There are still some fires.
There is no information yet on whether animals were injured.
According to its spokesman, the Cologne Zoo was already closed when the fire brigade received the alarm.
The Kölner Stadtanzeiger reports that smaller monkeys as well as snakes and birds are housed in the tropical house.