Four orangutans at the Denver Zoo found their way into a secured hallway outside their bedrooms Wednesday afternoon after a supposed door malfunction.

Zoo officials said the incident, which began at about 3:30 p.m. Wednesday afternoon, started when a door connecting the apes’ bedrooms to a secured, side hallway used by animal care specialists and veterinarians to work with the orangutans malfunctioned, leading to four of the primates going into the hallway, Denver Zoo Director of Integrated Communications Jake Kubié said Friday.

“Definitely at no point did they have access to any other areas of the facility, certainly not to the outside of their exhibit,” said Kubié.

Upon learning the apes had escaped their bedrooms, veterinarians made sure that the orangutans were contained in the hallway before sedating them using dart guns, Kubié said. Then, once the primates were asleep, they were picked up and returned to their living spaces.

“The orangutans are very comfortable with the people who take care of them, but they can still be a dangerous animal,” Kubié said. “We were very cautious not to have contact with the animals.”

Male orangutans can be up to 6 feet tall, and can weigh up to 200 pounds, with the largest reaching 250 pounds, according to the Denver Zoo’s website. Female orangutans are typically 3 to 4 feet tall, with most weighing up to 110 pounds and some reaching 150 pounds. 

The empty hallway did not contain any supplies or materials that could potentially harm the orangutans, which are kept in another part of the area, Kubié said.

The faulty door in question is custom-made and designed specifically for orangutans in that area, Kubié added.

The zoo will conduct an internal review of what malfunction occurred and will change infrastructure or security protocols to prevent such events from happening again in the future.