A colony of chimpanzees went on a picnic of sorts at a zoo here Sunday afternoon, forcing the evacuation of several thousand visitors.

About 30 chimps slipped out of their outdoor enclosure at the Chester Zoo about lunchtime and invaded the area where keepers prepared their food.

"Somehow or other they got into the kitchen - it must have been the smell of the bananas or something like that," zoo director Gordon McGregor told the BBC. "It was a bit like an old-fashioned chimps tea party... they've certainly had a ball in that room that's for sure."

McGregor said the chimpanzees went through "a lot of food."

When the animals were discovered in the keeper area, zoo staff initially hid the 5,000 visitors in other buildings, according to the Daily Mail. Shortly afterward, the visitors were escorted from the grounds and offered refunds.

The chimps were never in any public areas. It isn't known how they escaped.

The 111-acre zoo was ranked by Forbes magazine in 2007 as one of the best 15 zoos in the world.