San Francisco ? The director of the zoo where a teenager was killed by an escaped tiger acknowledged Thursday that the wall around the animal’s pen was just 12 1/2 feet high – well below the height recommended by the accrediting agency for the nation’s zoos.

San Francisco Zoo Director Manuel A. Mollinedo also admitted that it is becoming increasingly clear the 350-pound Siberian tiger leaped or climbed out of its open-air enclosure, 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 have ruled out the theory 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 16.4 feet high. But Mollinedo said the nearly 70-year-old wall was 12 feet, 5 inches high, with what he described as a “moat” 33 feet across.

He said safety inspectors had examined the 1940 wall 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 the “moat” contained no water, and has never had any. He did not address whether that affected the tiger’s ability to get out.

Based on the earlier, incorrect height estimate, animal experts had expressed disbelief that a tiger in captivity could have made such a spectacular leap.

“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 who makes frequent television appearances, said late Thursday. “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. I don’t think it would ever just do it to do it. Somebody had to have provoked it.”

Another tiger expert remained skeptical.

“It all depends on the surface and whether they could climb up it,” said John Seidensticker, head of the Conservation Ecology Center at the Smithsonian National Zoological Park. “I really don’t think a tiger could spring that high. A leopard could. A leopard could in a minute.”

Seidensticker emphasized that he has not seen the San Francisco Zoo’s tiger enclosure.

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.

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.”

Feldman would not comment on how difficult it would be for a tiger to scale a 12 1/2-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, who is director of conservation at the Minnesota Zoo and the big-cat expert who sets safety standards for tiger exhibits at North American zoos.

Many other U.S. zoos have significantly higher walls around their tigers.

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. Brothers Paul Dhaliwal, 19, and Kulbir Dhaliwal, 23, were at San Francisco General Hospital with severe bite and claw wounds.

Their names were provided by hospital and law enforcement sources who spoke on condition of anonymity because the family had not yet given permission to release their names.