The director of a zoo where an escaped tiger killed a teenager and mauled two others during a Christmas rampage has admitted that the animal’s enclosure was well under the height recommended by the national accrediting agency.

The director of San Francisco Zoo, Manuel A. Mollinedo, also acknowledged yesterday that the rare Siberian tigress must have leaped or climbed out of the open-air enclosure, possibly by gripping onto a ledge.

“She had to have jumped,” he said. “How she was able to jump that high is amazing to me.”

Mr Mollinedo was forced to backtrack on an earlier claim that the walls of the enclosure were 18 feet (5.5 metres) high after it emerged that they were in fact just 12 feet, 5 inches (3.8 metres), considerably under the minimum height of 16.4 feet (5 metres) recommended by the Association of Zoos and Aquariums.

Experts had ealier expressed disbelief that a captive tiger could make such a spectacular leap, a position that is now being revised.

“Before I said it was impossible, that’s what I’ve said for the last two days,” Jack Hanna, a former director of the Columbus Zoo and regular television commentator, said last night. “But today, I don’t know if I’d use the word impossible.

“I think it could be feasible for a cat that has been taunted or angered,” Mr Hanna added. “I don’t think it would ever just do it to do it. Somebody had to have provoked it.”

Police, who have declared the big-cat exhibit a crime scene, are investigating the possibility that someone may have taunted the animal.

Police Chief Heather Fong said a shoeprint was found on the railing of the fence surrounding the enclosure and that it was being checked against the shoes of the three victims.

She also revealed that the dead teenager, Carlos Sousa Jr, 17, spent the final moments of his life trying to save his friend from a brutal mauling by the 350-pound tiger.

Tatiana, a four-year-old Siberian tigress, went on her deadly rampage shortly before closing time on Christmas Day, at first targeting Kulbir Dhaliwal, 23, Ms Fong said.

As the tiger clawed and bit him, Mr Sousa and Mr Dhaliwal’s younger brother Paul, 19, shouted in the hope of scaring it off. The cat then turned its attention to Mr Sousa, killing him with a slash to the neck as the brothers ran to the zoo’s café for help.

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