Contractors are completing work on the lion and tiger enclosures, the San Francisco Chronicle reported. When the exhibit reopens to the public, scheduled for Feb. 7, the tigers will be surrounded by wire mesh 19 feet high.

The new defenses at the zoo include surveillance cameras in areas where dangerous animals are kept, electronic alarms for escapes and moats with wires that carry a light electrical charge to shock would-be escapees.

The Siberian tiger that escaped on Christmas Day also mauled two brothers. At the time, zoo officials suggested that one or more of the three might have provoked the escape and attack.

At a public hearing Monday, Nick Podell, chairman of the San Francisco Zoological Society, said the three couldn't be blamed for the attack even if they did something.

"Under no circumstances is it OK for an animal to escape its enclosure," he said. "I want to deliver a mea culpa for the zoo. There is no excuse."