Animal care and services personnel in San Jose, California, are investigating the circumstances surrounding the mauling deaths of four Miniature Horses and a Sicilian donkey at a zoo there.

Charlotte Orr, conservation and communications manager for the Happy Hollow Park & Zoo, said that on Jan. 15 zoo personnel discovered the remains of a Miniature stallion in his stall adjoining a paddock enclosed by a four-foot fence. The horse had ostensibly been mauled by another animal.

Surveillance video showed three dogs in the park, and staff identified where they might have gained entry by digging under a gate, Orr said.

Following the incident, zoo administrators increased nighttime patrols and moved three other Miniature Horses and a Sicilian donkey to another paddock with a six-foot fence, she said. However, on Jan. 20 officials found those animals dead, also apparently mauled