NEWARK, N.J. -- Delta Airlines says it is investigating the death of a dog on board one of its planes, CBS New York reports.

The dog's owners were flying from Phoenix to Newark. The 8-year-old Pomeranian named Alejandro was found dead inside its cage in a cargo hold Wednesday.

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.

There were at least 4 dog deaths while in the care of U.S. airlines this year. 

In 2017, according to data from the Department of Transportation, out of the 506,994 animals transported by U.S. airlines, there were 24 pet deaths, 15 injured and one loss. Eighteen of the dead and 13 of the injuries were on United. Delta had two deaths and one injury.  

This year, in February, a bulldog died of unknown causes on Hawaiian Airlines, and in March, a German Shepard died of natural causes a Delta flight. And a dog died in the overhead bin on a United flight in March.

In May, United said it would no longer accept 21 breeds of dogs and four breeds of cats considered high-risk due to respiratory issues. The affected breeds include boxers, pugs and Boston terriers. American, Delta, and other airlines had already refused to ship those breeds.

Continue reading at CBSNews.com.