It has closed the exhibit for the moment, but this is to facilitate investigations into the incident rather than for safety reasons, it said.
A moat separates the tigers from the visitors' bridge by 8.5m at the nearest point, and by 10m at the furthest.
The centre of the moat, its deepest portion, is 1.75m deep, while water on either side comes up to 1.5m. The fences on the sides of the enclosure are 5.8m high, and those at the back, 4.7m high.
Another 1.5m-high hot-wire fence stands in front of the 4.7m fence as an additional precaution.
These measurements 'conform to international safety guidelines imposed by the Association of Zoos and Aquariums', said Mr Biswajit Guha, the zoo's assistant director of zoology.
He pointed out that regular safety audits are held, with the last done on Sept 11. Only minor defects, such as rust on the fences and overgrown vegetation, were found, and rectified.
'In view of the permanent safety features, there is no risk to any visitor or zoo staff at any time,' he added.
LEE HUI CHIEH