One person has been killed and two others injured after a tiger escaped from its cage at San Francisco Zoo.
All of the victims were visitors to the zoo, a spokesman for San Francisco emergency services said.
It is not clear how the tiger, which was shot dead during the rampage, escaped from its pen.
The incident occurred in a cafe as the zoo was closing at around 1700 (0100 GMT). Local media initially incorrectly reported that four tigers had escaped.
Emergency services spokesman Lt Ken Smith said that they were called to the zoo at 1715 following a report that a person had been attacked by a tiger.
In response the zoo was evacuated and armed police officers and firefighters sent to the scene.
Police shot the tiger as it was mauling one of the victims who survived, Lt Smith said.
The two injured people were described by Lt Smith as being in a critical condition.
Margie Shafer, a reporter from local radio station KCBS, told the BBC that the attack occurred when the tiger entered the Terrace Cafe, a restaurant about 60m (yards) from the tiger enclosure.
She said that there were unconfirmed reports that the tiger had jumped a moat to make its escape.
San Francisco Zoo is home to both Siberian and Sumatran tigers.
In December 2006, a keeper at the zoo had her arm severely lacerated when a female Siberian tiger reached through the bars of its cage and mauled her during a public feeding.
As a result of that attack the zoo built a new feeding enclosure in its Lion House to protect the trainers as they carried out feedings.