London Zoo says it believes Melati carried the cub outside, but keepers are unclear as to how the cub got into the pool.
Keepers are now reviewing the situation because it was not forseen that the mother would take the cub outside so early.
More top news
Sir Bruce entertained audiences for more than seven decades.
Work in the tower will also pause over the bank holiday weekend.
The attacker grabbed her dog lead wrapped it round her neck and started to strangle her before running away.