NEW YORK (CBSNewYork/AP) — A criminal investigation has been launched into the death of a French bulldog puppy on a United Airlines flight after its owners say a flight attendant ordered the dog to be placed in the plane’s overhead bin.

In a statement issued late Wednesday, the Harris County, Texas, district attorney’s office said its animal cruelty division is working with the county’s animal cruelty task force to investigate the incident.

The statement said prosecutors won’t decide if criminal charges are warranted until the investigation is completed.

It was on a Monday flight from Houston to New York when 11-year-old Sophia Ceballos and her mom, Catalina Robledo, say they were told by a flight attendant that their dog Kokito, which was in a carrier, had to be put in an overhead bin for flight.

“I was like, ‘It’s a dog, it’s a dog. He can’t breathe up there.’ And she was like, ‘It doesn’t matter,'” Sophia said.”She felt the dog and just put him up there.”

The family says they heard Kokito barking for two hours. They say they wanted to check on him, but couldn’t.

“We tried, but there was a lot of turbulence and we weren’t allowed to stand up,” Sophia said.

When they landed at LaGuardia, Kokito was dead.

“My mom was crying. She was just screaming, she was looking at him,” Sophia said.

United acknowledged Wednesday that the customer said there was a dog in the carrier.

“However, our flight attendant did not hear or understand her, and did not knowingly place the dog in the overhead bin,” the airline said in a statement. United declined to identify the employee.

In a separate incident, the Swindle family was supposed to be flying their dog, Irgo, from Oregon to Kansas City on a United flight Tuesday.

The dog flew from Oregon to Denver, where he spent the night. The next day, he was scheduled to fly to Kansas City to be reunited with his family when they went to pick up Irgo from the airport.

“They showed me the kennel and the minute I said the word, ‘Irgo,’ out pops this Great Dane,” said Irgo’s owner, Kara Swindle.

Irgo was mistakenly switched with another dog and put on a flight to Japan. United says Irgo made it to Japan safely and is expected to be reunited with his family in Wichita sometime Thursday night.

In a statement to CBS affiliate KCTV, United said “an error occurred during connections in Denver for two pets sent to the wrong destinations.”

“We have notified our customers that their pets have arrived safely and will arrange to return the pets to them as soon as possible. We apologize for this mistake and are following up with the vendor kennel where they were kept overnight to understand what happened.”

As for Monday’s incident with Kokito, United called it “a tragic accident that should never have occurred, as pets should never be placed in the overhead bin. We express our deepest condolences.”

Last year, 18 animals, mostly dogs, died while being transported on United — three-fourths of all animal deaths on U.S. carriers, according to the Department of Transportation. Those figures represent animals that die in cargo holds.

It is rare that an animal dies on a plane. Even on United there was only one death for roughly every 4,500 animals transported last year.

United, which promotes its pet-shipping program called PetSafe, carries more animals than any other airline, but its animal-death rate is also the highest in the industry. Alaska Airlines, which carries only 17 percent fewer animals, had just two deaths last year.

“The overwhelming majority (of deaths), according to medical experts, were due to a pre-existing medical condition or the animal wasn’t properly acclimated to its crate,” said United spokesman Charles Hobart.

Hobart said the airline investigates every injury or death to an animal in its care. Pets are loaded last and taken off the plane first after landing, he said.

By next month, United officials say they will be issuing bright yellow tags to passengers traveling with pets in carriers.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)