ORLANDO, FLA.—SeaWorld Orlando says a beluga whale died shortly after it was born at the theme park and an investigation has begun into the cause of death.

The Orlando Sentinel reports that theme park officials say the calf was born this past week but was unusually weak and rose to the surface briefly before sinking to the bottom of a pool. Its mother was 17-year-old Whisper, who has lived at SeaWorld Orlando since 2010.

SeaWorld said animal care teams tried to revive the calf, but were unable to save it. The cause of the newborn whale’s death is unclear.

Park officials say they will run a full post-mortem examination, which could take several weeks before results are finalized. They also say Whisper’s pregnancy appeared normal.