US tiger death zoo a crime scene

The injured victims are now described as stable

The American zoo where a tiger killed one man and injured two on Christmas Day has been declared a crime scene.

Police in San Francisco are now said to be investigating the possibility that the victims taunted the tiger, or even helped it escape from its enclosure.

The San Francisco Chronicle says blood and a shoe were found near a moat which separated the tiger from the public.

The 300lb (136kg) animal, named Tatiana, was shot dead as she loomed over one of the injured men.

Zoo officials say they are baffled as to how the Siberian tiger got out of her enclosure, which is surrounded by a 15ft (4.5m) wide moat and a 20ft (6m) high wall.

They say the gate to the enclosure was closed, and zoo director Manuel Mollinedo says the tiger may have been provoked.

"Somebody created a situation that really agitated her and gave her some sort of a method to break out," he said.

There was no way out through the door. The animal appears to have climbed or otherwise leaped out of the enclosure Robert Jenkins, zoo director

The zoo itself will be remaining closed on Thursday as police continue their investigation.

The body of the dead man, Carlos Sousa, 17, from San Jose, was found with a gaping throat wound outside the tiger's enclosure.

His two friends, whose names have not yet been made public, were found badly injured 300m away.

Police believe the tiger followed the trail of blood they left and was preparing to attack one of them again when police shot her dead.

Tatiana attacked one of the zoo's keepers last year

The attack happened just before closing time, and for some hours police hunted through the zoo in the deepening gloom in the belief that more wild animals could have been free.

The injured men, brothers aged 19 and 23, and also from San Jose, are said to be in a stable condition, but have deep bites and claw wounds on the heads, necks, arms and hands. Doctors say they expect them to make a full recovery.

San Francisco Zoo is home to Siberian and Sumatran tigers.

In December 2006, a keeper at the zoo had her arm severely lacerated when Tatiana reached through the bars of her cage and mauled her during a public feeding.

As a result of that attack the zoo built a new feeding enclosure in its Lion House to protect the trainers as they carried out feedings.