The San Francisco Zoo was closed to visitors Wednesday as investigators tried to determine how a tiger escaped from its enclosure and attacked three visitors, killing one of the men and mauling two others.
Officials planned to conduct a thorough sweep of the zoo grounds during daylight. They said additional victims were not likely but they were uncertain how long the tiger, a female named Tatiana, had been loose near closing time on Christmas Day before she was killed by police.
Tatiana, a Siberian tiger weighing about 300 pounds, was the same animal that ripped the flesh off a zookeeper's arm just before Christmas 2006.
The three men _ one of them 19 years old and the others in their early 20s were attacked just after 5 p.m. Tuesday on the east end of the 125-acre zoo grounds near Ocean Beach, police spokesman Steve Mannina said.
They suffered ``pretty aggressive bite marks,'' Mannina said.
The two injured men were in critical but stable condition Wednesday at San Francisco General Hospital after undergoing surgery to have their wounds cleaned and closed, authorities said. They suffered deep bites and claw cuts on their heads, necks, arms and hands.
The San Francisco medical examiner had not been able to identify the dead man, investigator Tim Hellman said Wednesday. The man did not have any identification and no one had called asking about him, according to Hellman.
The zoo's director of animal care and conservation, Robert Jenkins, could not explain how Tatiana escaped. The tiger's enclosure is surrounded by a 15-foot-wide moat and 20-foot-high walls, and the big cat did not leave through an open door, he said.
``There was no way out through the door,'' Jenkins said. ``The animal appears to have climbed or otherwise leaped out of the enclosure.''
The first attack happened right outside the Siberian's enclosure _ the victim died at the scene. A group of four officers came across his body when they entered the dark zoo grounds, Mannina said.
The second victim was about 300 yards away, in front of the Terrace Cafe. The man was sitting on the ground, blood running from gashes in his head and Tatiana sitting next to him.
The cat attacked the man again, Mannina said. The officers approached the tiger with their handguns. Tatiana moved in their direction and several of the officers fired, killing the animal.
Only then did they see the third victim, who had also been mauled.
Although no new visitors were let in after 5 p.m. Tuesday, the grounds had not been not scheduled to close until an hour later, and 20 to 25 people were still in the zoo when the attacks happened, zoo officials said. Employees and visitors were told to take shelter when zoo officials learned of the attacks.
``This is a tragic event for San Francisco,'' Fire Department spokesman Lt. Ken Smith said. ``We pride ourselves in our zoo, and we pride ourselves in tourists coming and looking at our city.''
There were five tigers at the zoo _ three Sumatrans and two Siberians. Officials initially worried that four tigers had escaped, but soon learned only Tatiana had escaped, Mannina said.
On Dec. 22, 2006, Tatiana reached through the bars of her cage and grabbed a keeper, biting and mauling one of the woman's arms and causing deep lacerations. The zoo's Lion House was temporarily closed during an investigation.
California's Division of Occupational Safety and Health blamed the zoo for the assault and imposed a $18,000 penalty. A medical claim filed against the city by the keeper was denied.
Last February, a 140-pound jaguar named Jorge killed a zookeeper at the Denver Zoo before being fatally shot. Zoo officials said later that the zookeeper had violated rules by opening the door to the animal's cage.
After last year's attack, the zoo added customized steel mesh over the bars, built in a feeding shoot and increased the distance between the public and the cats.
Tatiana arrived at the San Francisco Zoo from the Denver Zoo a few years ago, with zoo officials hoping she would mate with a male tiger. Siberian tigers are classified as endangered and there are more than 600 of the animals living in captivity worldwide.
