SAN FRANCISCO — Nine days after a tiger mauled three visitors, the San Francisco Zoo reopened Thursday amid heightened scrutiny of its security procedures and a flurry of questions over the events that led to a teenager's death.

The big cat enclosure where a 350-pound Siberian tiger escaped Christmas Day was closed and will remain so indefinitely, while visitors Thursday found a new public alert system and more signs around the facility warning people not to pester the animals.

The improvements were made as police investigated whether the victims had taunted the tiger before it climbed or leaped out of its outdoor pen. Carlos Sousa Jr., 17, was killed, and his two friends were severely injured.

"All I know is that something happened to provoke that tiger to leap out of her exhibit," zoo director Manuel Mollinedo said Wednesday. He declined to elaborate because the police investigation continued.

A woman has claimed she saw three men teasing the lions shortly before the tiger attack, according to a report on the Web site of the San Francisco Chronicle. Jennifer Miller, who was at the zoo with her husband and two children, said the family left the area because her kids were disturbed by the young men's behavior.

"The boys, especially the older one, were roaring at them. He was taunting them," Miller told the newspaper.

Police talked to Miller on Wednesday, but were not able to corroborate reports that the victims taunted the tigers, Inspector Valerie Matthews said. They also could not substantiate Miller's claim that a fourth person was with the attack victims, or what effect the taunting she described might have had.

"I don't know if what they did was any more than what kindergartners do at the zoo every day," Matthews told the Chronicle.

Sgt. Steve Mannina, a police spokesman, said investigators found an empty vodka bottle on the front seat of the car the victims drove to the zoo. Police were looking into whether alcohol was a factor in the attack.

"They did find the bottle, but what that signifies or how that plays into this will be known later," Mannina said.

Toxicology tests on Sousa's body have not been completed yet, and results likely will not come back for several weeks, according to the San Francisco medical examiner's office.

Miller said Sousa, whom she later recognized in newspaper photos, was not harassing the animals.

Mark Geragos, an attorney for the survivors — brothers Kulbir Dhaliwal, 23, and Paul Dhaliwal, 19 — said he did not think a vodka bottle was recovered from the car. He also said none of the victims did anything to goad the tiger into breaking loose.

"That's just nonsense," Geragos said. "There is no evidence of taunting whatsoever because there was no taunting."

Earlier this week, he said the zoo was slow in its response to the escaped tiger, an assertion at least partially backed up by police dispatch logs showing that employees initially questioned whether early reports of the attack were coming from a mentally unstable person.

Geragos said his clients tried to get help for Sousa, but were denied entry to a cafe where they had fled because the zoo was closing.

The brothers then spotted a female security guard who appeared diffident when told of the escaped tiger, Geragos said. Sousa was still outside the tiger exhibit, mortally wounded with a slashed throat.

Mollinedo brushed off Geragos' claims, saying he was satisfied with the employees' response.

"Some of our staff did heroic things, and I hope that eventually they can be recognized for the way they handled some very difficult situations where they actually put their lives on the line," he said.

Mollinedo declined to elaborate, citing the investigation. He said he did not know how many employees were on the grounds when the tiger, named Tatiana, escaped.

None of the zoo's lions or tigers were to be on view Thursday.

Zoo officials say the tiger likely climbed out of an empty moat that separated the public from the animal's enclosure, which had a 12 1/2-foot wall, making it 4 feet shorter than the recommended minimum height for U.S. zoos.

The city has hired an architect to design a new, more secure pen that would put a 19-foot-tall barrier between visitors and the zoo's big cats, Mollinedo said Wednesday.


Associated Press writers Paul Elias and Marcus Wohlsen contributed to this report.