NEWARK, N.J. (CBSNewYork) – Delta Airlines says it is investigating the death of a dog on board one of its planes.

The 8-year-old Pomeranian named Alejandro was found dead inside its cage in a cargo hold Wednesday.

The dog’s owners were flying from Phoenix to Newark.

During a layover in Detroit, Alejandro was fine. But when airline employees checked two hours later, they found him dead.

Delta said it knows pets are important members of the family and is working with the owners to find out what happened.