SAN FRANCISCO - The director of the zoo where a teenager was killed by an escaped tiger acknowledged yesterday that the wall around the animal's pen was just 12 1/2 feet high - about four feet below the height recommended by the accrediting agency for the nation's zoos.

San Francisco Zoo Director Manuel Mollinedo also admitted that it was becoming increasingly clear that the 300-pound Siberian tiger had leaped or climbed out of its open-air enclosure, perhaps by grabbing on to a ledge.

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

Mollinedo said investigators have ruled out the theory that the tiger escaped through a door behind the exhibit.

According to the Association of Zoos & Aquariums, the walls around a tiger exhibit should be at least 16 feet, 4 inches high. But Mollinedo said the nearly 70-year-old wall was 12 feet, 5 inches, with what he described as a "moat" 33 feet across.

He said that three years ago safety inspectors examined the wall, erected in 1940, and did not raise a fuss about its size.

Mollinedo said the "moat" contained no water and has never had any. He did not address whether that affected the tiger's ability to get out.

On Wednesday, the zoo director said that the wall was 18 feet high and the moat 20 feet wide. Based on those earlier, incorrect estimates, animal experts expressed disbelief that a tiger in captivity could have made such a spectacular leap.

AZA spokesman Steven Feldman said that the minimum height is just a guideline and that a zoo could still be deemed safe even if its wall were lower.

Feldman would not comment on how difficult it would be for a tiger to scale a 12 1/2-foot-wall. But Siberian tigers are known to have phenomenal strength, at least in the wild.

"There are rare glimpses of this in the real world that suggest, when taunted, tigers can be fairly extraordinary in their physical feats," said Ronald Tilson, director of conservation at the Minnesota Zoo and the big-cat expert who sets safety standards for tiger exhibits at North American zoos.

The animal, a female named Tatiana, went on a rampage near closing time on Christmas Day, mauling three visitors before it was shot to death by police. Carlos Sousa Jr., 17, died and two brothers, ages 19 and 23, suffered severe bite and claw wounds.

The San Francisco Chronicle, citing anonymous sources, reported yesterday that police are investigating whether or not the victims taunted the tiger. *