NEW YORK (CBSNewYork/AP) — A dog died on a United Airlines plane after a flight attendant ordered its owner to put the animal in the plane’s overhead bin.

United said Tuesday that it took full responsibility for the incident on the Monday night flight from Houston to New York.

In a statement, United called it “a tragic accident that should never have occurred, as pets should never be placed in the overhead bin.”

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The 10-month-old French Bulldog puppy was in a small pet carrier designed to fit under an airline seat.

Passengers reported that they heard barking during the flight and didn’t know that the dog had died until the plane landed at LaGuardia Airport. The owner, traveling with her two children, opened the pet carrier to find the animal dead.

The woman’s husband tells CBS2 it was the family’s third time flying with the animal, but never like this.

“She was reluctant to put it in the overhead bin,” Brayan Castano said. “This seemed odd to my wife, being that it’s such a tight space.”

“It’s on them that the dog died,” LaGuardia traveler Nikki Bonilla said of the airline. “It’s a live dog, you just don’t put a live dog up there.”

Passenger Maggie Gremminger posted a photo on Twitter of the dog’s owner and children after the flight. “I want to help this woman and her daughter. They lost their dog because of an @united flight attendant. My heart is broken,” she wrote.

“I’d give it the same situation like leaving a child in a car,” LaGuardia traveler Kyle Cook said. “You’re not going to lock them in a small area for too long, so same ideas as that. Why would you put a dog inside a small area for a long period of time.”

United spokesman Charles Hobart said the flight attendant told the dog’s owner to put the pet carrier in the overhead bin because the bag was partly obstructing the aisle. It is unclear why the carrier was not placed under a seat, he said.

The flight attendant is said to be distraught, as a language barrier may have added to the confusion precipitating the dog’s death, CBS News’s Kris Van Cleave reported. Sources tell CBS News the flight attendant claims she wasn’t aware there was a dog inside the bag.

Hobart said United is investigating the incident and talking to the flight attendant, whom he declined to identify. He said the airline refunded the tickets purchased for the dog owner and her two children and the fee that they paid to bring a pet on board — typically $200.

The cause of the dog’s death was not immediately known. The spokesman said Chicago-based United offered to pay for a necropsy.

Animal rights groups have called for swift action.

“If reports are true that a United Airlines flight attendant insisted that this dog’s guardian put him in the overhead bin, then he or she should be fired and charged with cruelty to animals for this dog’s horrific, terrifying death,” PETA said in a statement sent to CBS2.

Last year, 18 animals died while being transported on United — there were six cases on all other U.S. carriers combined, according to the Department of Transportation.

United has suffered a string of incidents that generated bad publicity in the last two years, including the violent removal of a passenger from a United Express plane to make room for a crew member, and the death of a giant rabbit — its Iowa owners sued the airline, which they said cremated the animal to destroy evidence about the cause of death.

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)