A staff member holds a red panda that was born at the Edmonton Valley Zoo in 2009. This is not the same animal that died on Thursday. ((CBC))

One of the red panda cubs at the Edmonton Valley Zoo has died.

The zoo said Friday that the nine-week-old panda had a blood clot that extended into the airways of its lungs. It stopped breathing on Thursday.

"We had a very, very healthy, vibrant, thriving young panda, which I had examined the day before, doing well," said zoo veterinarian Dr. Milton Ness.

"Basically doing well right up until she was put down for the night. [She] woke up at the wee hours of the morning and basically had passed away within 15 minutes."

The red panda and her twin brother, which is still alive, were born at the zoo on July 5.

It was one of six pandas that were part of the zoo's international species survival plan.

The cubs were being hand-raised by an animal health technologist.