Leanne, the endangered Sumatran tiger that gave birth last week at the San Francisco Zoo, was hiding a surprise for the zoo-keepers. It seems that the tiger mom had triplets.

It is the first birth of Sumatran tiger for the zoo since 1956.

The 230-pound tiger was supervised with a video camera from the first day she gave birth. But she licked the camera, so the vision was altered.

“Leanne has been excellent at tending to her litter and she has managed to keep them hidden from our camera, which had made it difficult for us to determine how many cubs really were in the nest box....in addition, she managed to lick the camera lens at one point, slightly blurring our view,” said Jacqueline Jencek, chief zoo veterinarian.

But when Leanne got out of the shelter to drink water, one of the keepers saw there were three babies in the nesting box.

"When we physically confirmed two more cubs, everyone was just ecstatic with news of the triplets," the veterinarian said, according to The Mercury News.

The zoo staff hopes to be able to examine the newborn cubs in a few days.

As the tiger species is endangered, the mother, Leanne, and the father George were loaned for breeding, from an aquarium in Denver and a zoo in San Antonio, the Associated Press informs.

The same zoo where the triplets were born became famous around Christmas, when an escaped tiger attacked three boys, killing one of them. The tiger was immediately shot.