Police are today reportedly investigating whether one or more of the young men mauled by a tiger at the San Francisco Zoo may have taunted the animal.

The big cat exhibit at San Francisco Zoo was cordoned off as a crime scene today as investigators probed whether a 21-stone Siberian tiger that killed a visitor escaped from its high-walled pen on its own, or was let out deliberately.

A tiger escaped from its pen at the San Francisco Zoo today, killing one man and critically injuring two others before police shot it dead, authorities said.