SAN FRANCISCO - The director of the San Francisco Zoo, where a teenager was killed by an escaped tiger, acknowledged Thursday that the wall around the tiger's pen was just 121/2 feet high - well below the height recommended by the main accrediting agency for U.S. zoos.

The zoo director, Manuel A. Mollinedo, also said it was becoming increasingly clear that the 300-pound Siberian tiger leaped or climbed out of her open-air enclosure Christmas Day, perhaps by grabbing onto a ledge.

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

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

According to the Association of Zoos and Aquariums, the walls around a tiger exhibit should be at least 16.4 feet high. But Mollinedo said the wall at the zoo's big-cat enclosure was 12 feet, 5 inches, with a moat 33 feet across.

He said safety inspectors had examined the wall, which dates to 1940, and never raised any red flags about its size.

"When the AZA came out and inspected our zoo three years ago, they never noted that as a deficiency," he said. "Obviously now that something's happened, we're going to be revisiting the actual height."

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

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

Accreditation standards require "that the barriers be adequate to keep the animals and people apart from each other," Feldman said. "Obviously, something happened to cause that not to be the case in this incident."

Many other U.S. zoos have significantly higher walls around their tigers. The Philadelphia Zoo said it had 16-foot walls topped with a 3-foot overhang. At the Bronx Zoo, the tigers are surrounded by a 20-foot-high chain-link fence with a 5-foot overhang that curls inward at the top. An electrified wire runs along the inside of the fence.

Feldman would not comment on how difficult it would be for a tiger to scale a 121/2-foot wall. 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 San Francisco tiger, Tatiana, went on a rampage near closing time Tuesday, mauling three visitors before she was shot to death by police. Carlos Sousa Jr., 17, of San Jose, died and two unidentified San Jose brothers, ages 19 and 23, suffered severe bite and claw wounds.

Police are still investigating and have declared the big-cat exhibit a crime scene.

The San Francisco Chronicle, citing anonymous sources, reported Thursday that police were looking into the possibility that the victims had taunted the tiger and dangled a leg or other body part over the edge of the moat. The newspaper said police had found a shoe and blood inside the enclosure.

At a news conference Thursday, Police Chief Heather Fong said police had no information that anyone had put a leg over the railing, and she said no shoe was found in Tatiana's enclosure. She did not address whether the victims had teased the tiger.

She said that a shoe print was found on the railing of the fence surrounding the enclosure and that police were checking it against the shoes of the three victims.

The dead teen's father, Carlos Sousa Sr., said Thursday: "Right now, what I want to know is if it was taunting, who did it? Why wasn't this protected right? I want some answers."

The AZA said in a statement that this was the first time a visitor had been killed because of an animal escape at an AZA-accredited zoo.

Jim Maddy, the AZA's president and chief executive, called the San Francisco facility "a great zoo" and said it had the association's support.

Mollinedo said surveillance cameras and new fencing would be installed around the tiger exhibit. The zoo will remain closed Friday.