Keepers seek to raise cubs after red panda died unexpectedly at Chattanooga Zoo [photos]

Maina, an endangered red panda who recently bore two sons and has lived at the Chattanooga Zoo since 2014, died unexpectedly Saturday.

No one knows the cause of death, said Chattanooga Zoo CEO and President Dardenelle Long during a news conference Thursday.

Maina, 3, seemed healthy. She had been nursing her two 3-month-old cubs and all seemed well Saturday morning.

But later that day, zoo employees found Maina lying lifelessly in the outdoor red panda exhibit.

Employees immediately attempted CPR and rushed her to the Regional Institute for Veterinary Emergencies and Referrals (RIVER) animal hospital in hopes of reviving her, but it was too late, Long said.