Zoo officials said there is also a mesh barrier beyond the railing, but Kraus said it was designed to catch small objects such as cameras, and not humans.
Steve Feldman, a spokesman for the Association of Zoos and Aquariums, said no one he's spoken to can recall any deaths of children at an accredited zoo over the last 40 years or more. Feldman said the Pittsburgh Zoo successfully completed its five-year review in September, which means it meets or exceeds all safety standards.
In May, some of the dogs crawled under a fence and escaped into a part of the exhibit that's usually closed. The zoo was on lockdown for about an hour as a precaution.
Past fatal attacks at zoos have prompted zoos around the nation to review safety features of their exhibits. In 2007, a tiger jumped over a wall at the San Francisco zoo, killing one visitor and wounding two others. In September a man jumped off an elevated viewing train at the Bronx Zoo in New York and was severely mauled by tigers.
Baker said the Pittsburgh Zoo has never had a visitor death. She said no decision has been made yet on the future of the exhibit.
Associated Press writer Ron Todt in Philadelphia contributed to this report.