WATCH: 7 Puppies DEAD After American Airlines Flight To Chicago, Airlines Investigating

Seven out of 14 puppies that shipped on an American Airlines flight Wednesday morning are now dead.

The flight, which came from Tulsa to Chicago, arrived at O'Hare at 8:54 a.m. Wednesday. Five of the puppies died immediately after landing, American Airlines spokeswoman Mary Frances Fagan told CBS 2.

Two more dogs died at the veterinarian's office.

The airlines has launched an investigation into the matter, as the Chicago Tribune reported:

"We still have to talk to the employees who handled them. We plan to do that today," Fagan said. "They may have arrived alive, right now we don't know."

"We're going to figure out what happened. We've been transporting animals safely for 50 years. We do not want this happening again," Fagan said.

The puppies' cause of death is still unknown, although all the animals were described as looking "very lethargic" when they came off the plane, and workers were attempting to cool them off once they landed.

The Tribune places the total number of dogs onboard at 15, as opposed to CBS's 14.