Story highlights Chimps escape their pen pen for about 90 minutes

Zoo staff using treats lure the seven chimps back into their holding area

No one is injured during the escape

Seven chimpanzees at the Kansas City Zoo were smart enough to use a 6-foot-long tree branch to escape their enclosure on Thursday.

But they weren't smart enough to see through the old "Want a treat? Come get a cookie!" routine.

No chimpanzees or zoo patrons were injured during Thursday's brief escape.

Apparently one chimpanzee broke a 6-foot-limb off a tree and used it to scale a wall on the top of the outdoor enclosure, said Julie Neemeyer, a spokeswoman for the Kansas City Zoo in Missouri. The ringleader then enticed six other chimpanzees to join the fun, but they didn't get far.

Zoo staff used vehicles to block potential exits, then used treats to lure the animals back into their holding building. The incident lasted about 90 minutes, during which at least one TV station helicopter tracked one of the chimpanzees with its camera.

During the "code red" situation, some zoo patrons were kept inside some of the exhibits.

The chimps will get a day off Friday while zoo staff check the exhibit to see if there are any other tree limbs that might "create any issues," Neemeyer said.