The first Sumatran tiger cub to be born at the London Zoo in 17 years has died. The zoo confirmed the cub, which was born Sept. 22, died by drowning, likely in a pool inside the tiger enclosure.

According to the BBC, zookeepers monitoring the tiger den with cameras did not see the infant cub Saturday and when they went to check on the cub it was discovered lying on the edge of the pool within the tiger enclosure.

A post-mortem examination confirmed the cause of death as drowning. Only 21 days old, the tiger cub had not been named, nor had its gender been determined.

When the cub was born, zookeepers said they were nervous as it was the mother Melati's first cub. Zookeepers think Melati carried her cub outside the den, but it is unclear how the cub got into the pool; no cameras were in a position where that could be observed.

Zoo curator Malcolm Fitzpatrick said he was "heartbroken" over the loss, adding that in addition to Melati being a new mother, she also has a tendency to become a bit anxious. Zoo staff thought it was best not to alter her surroundings and allowed her to have full access to the tiger enclosure as normal, which may have inadvertently resulted in the drowning of the cub.

The cub was the "grandchild" of the Zoo's last tiger cub, Hari, the father of Melati, according to the BBC.

There are as few as 350 Sumatran tigers in the wild today, according to the Sumatran Tiger Trust, a non-profit tiger conservation group. About the same number of Sumatran tigers are kept in zoos around the world, the group said.

The rare birth of the Sumatran tiger cub was also celebrated because the event was captured on a hidden camera in the tiger den. That video (below) has been widely circulated on the internet.