DALLAS (AP/CBSDFW.COM) – A Dallas Zoo chimpanzee named Koko had to be sedated Tuesday after she briefly escaped her enclosure and got loose in an area not open to the public.

Sr. Cpl. Sherri Jeffrey says police were summoned around 10:20 a.m. Tuesday by zoo officials who said a large adult female chimpanzee had gotten loose.

Authorities closed the Wilds of Africa exhibit and moved visitors elsewhere in the complex as zoo workers quickly reached Koko in a building and tranquilized the animal.

“It never got out of the chimp building,” said Dallas Zoo Executive Director Gregg Hudson. “There were always at least two barriers between that animal and being released out, away from that building.”

Nobody was hurt.

Koko, a female in her twenties, escaped through an unsecured gate in what authorities called a sort of “bedroom” area. She was shot with a dart gun in a hallway.

“She wasn’t threatening, but she was trying to avoid the veterinarian with the tranquilizer gun,” said the Zoo’s deputy director Dr. Lynn Kramer.

Kramer said Koko knew she’d gone somewhere that she didn’t belong because she had climbed atop a 15-foot high cage.

“She was stressed and about half-a-dozen of her buddies were in the building vocalizing, and she wanted to get with them,” Kramer said.

It took about 15 minuets for the tranquilizer to take effect, and the animal was brought down without suffering an injury.

“She was about 15 feet in the air, so we put her in a sling and then lowered her down, put her in a bedroom and gave her a quick physical,” Kramer said.

Still, a Code Red was declared in the zoo because chimps are among 14 large animals deemed dangerous enough for extra precautions. Visitors to the Wilds of Africa exhibit were confused about why they were hurriedly shuffled out of the area.

“I didn’t know what was going on, whether it was routine maintenance or, not quite sure,” said Seth Wytrwal, who was visiting from Massachusetts.

In 2004, a male gorilla at the Dallas Zoo nambed Jabari cleared a 14-foot wall and mauled three people. The animal was killed by police.

“Actually, we did some physical changes in the building and some employee changes came out of that as well,” Hudson told reporters Tuesday.

Still, last year, another gorilla named Tufani escaped a holding area when an employee left a door open. Like Koko, Tufani never got into a public area. But Hudson said the Zoo is not taking the situation lightly and will determine what happened and how to prevent it in the future.

“Now we will go into the investigation and find out what happened on the unsecured door and why the chimp was able to access that,” he said.

Despite brief confusion, Zoo visitors said the incident wasn’t a harrowing or nerve-wracking experience.

“I figured if it was that big of a deal they’d shut down the whole park and not just one area,” visitor Erin Anders said. I “Never felt endangered or anything.”

(©2011 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)