The Toronto Zoo says the one surviving polar bear cub born at the zoo last week is fighting for its life in the intensive care unit.

Two cubs were born to mom Aurora at the zoo on Nov. 11 and in a news release issued Friday, the Toronto Zoo said one of the two cubs did not survive the first 24 hours. The second cub, zoo officials say, is now receiving 24-hour care.

“Aurora demonstrated good maternal instincts and her cubs did attempt to nurse, but it appears she was not producing any milk to feed her newborns,” said Eric Cole, Manager, Wildlife Care, said in a written statement accompanying the news release.

Medical staff will be providing the cub with intravenous fluids and feeding it a special milk formula.

"This is an extremely critical time for this tiny cub," Dr. Chris Dutton, Toronto Zoo’s Head of Veterinary Services, said in a written statement.

"In the cub’s first week, it faced a few significant challenges that required medical interventions but so far it appears to have responded very well to the treatments we provided.”