A young boy was killed yesterday after falling into an enclosure and being mauled by African wild dogs at a Pittsburgh zoo.

The boy, believed to have been a toddler, fell over a high railing and into the pen holding 11 African wild dogs.

The animals then attacked the boy.

Zoo head Barbara Baker said it was unclear if the boy was killed by the dogs, or from the fall.

"The keepers tried everything they could do. They responded immediately when visitors alerted them to the fact that a child was in the yard. They responded immediately and were able to get several of the dogs into the backup building. The veterinarians arrived and tried to scare the dogs away from the young child with darts and were unsuccessful in doing that. All of the dogs were eventually brought into the barn, into their backup building, except for one dog which the police shot."

An investigation has been launched into what went wrong.