Three newborn polar bears have died, according to officials at Toronto Zoo.

The three bear cubs were born on just Dec. 6, but have not survived their first week, tragically dying at the zoo.

In a news release Monday officials at Toronto Zoo have said that the three cubs, born to an 11 year old female polar bear called Aurora, died.

The three polar bear cubs were one female and two males; with one of the male cubs dying shortly after birth. The other two survived the birth, but both died on Sunday, according to the zoo.

The zoo has said at this time they do not know how the two cubs died on Sunday, but that tissue samples would have to be analyzed to find the cause of death.

The newborns were not the first for Aurora. The female polar bear gave birth to three other cubs last year as well, but officials at the zoo said that the mother rejected those three cubs last year. Of those three cubs only one survived in the long term.

The new cubs born this month, however, attracted the mother's attention, and zoo staff reported that she was showing maternal instincts not revealed last year.

Officials at the zoo are attempting to look on the bright side of events. Maria Franke, the zoo's curator of mammals, has said, "The fact that Aurora was doing everything right this time is a huge step in the right direction," according to CBC News.

There are only about 20,000 wild polar bears in the world today, making them officially “critically endangered.” About 60 percent of wild polar bears currently are in Canada.

The zoo has made a statement saying, "The information gained throughout Aurora's breeding has allowed us invaluable information that we can learn from and share with our counterparts."

The video below shows the polar bear cub at Toronto Zoo born last year in October 2011: