What to Know United Airlines said an attendant didn't knowingly put a dog in an overhead bin on a flight, even though the passenger told her as much

The dog, Kokito, died at some point during the flight from Houston to New York; his owner discovered the death after landing

Another passenger aboard the flight told NBC News that she heard the dog's owner mention that a dog was in the bag

United Airlines said Wednesday the flight attendant who ordered a passenger to put a dog in a carrier in an overhead compartment on a New York City-bound flight earlier this week "did not hear or understand" the mother's pleas not to put the pup in the bin.

The airline reiterated that it is taking full responsibility for the death of the 10-month-old French bulldog named Kokito, but added that the flight attendant didn't knowingly put the dog in an overhead compartment before the 4-hour, 25-minute flight from Houston to LaGuardia Airport Monday evening.

"We have learned that the customer did tell the flight attendant that there was a dog in the carrier," the airline said. "However, our flight attendant did not hear or understand her, and did not knowingly place the dog in the overhead bin. As we stated, we take full responsibility and are deeply sorry for this tragic accident. We remain in contact with the family to express our condolences and offer support."

It comes a day after the owner's daughter, 11-year-old Sophia Ceballos, told News 4 that her mother repeatedly said there was a dog in the carrier.

"My mom was like, 'It's a dog, it's a dog,'" said Ceballos, speaking for her mother Catalina Robledo, whose native language is not English. "And (the flight attendant) said, 'You have to put it up there."

A post shared by Kokito (@kokito_the_savage) on Jan 13, 2018 at 9:59pm PST

Maggie Gremminger, another passenger sitting nearby, also told NBC News she heard Robledo protesting with the attendant when she was asked to put the dog in an overhead compartment.

"The passenger there in the aisle seat then very specifically spoke to the fact that she didn't want to move (the bag) and that her dog was in the bag," she said.

Gremminger said other passengers seemed to hear Robledo say there was a dog in the carrier, adding that she thinks Robledo only relented and put the dog overhead "to avoid confrontation."

"It was a very triggering moment where it didn't feel right," Gremminger said. "The man to my right who was the other passenger that witnessed this, we actually kind of spoke about it. We looked at each other and said, 'Did they just put the dog up there?'"

Ceballos and Gremminger said they heard Kokito bark a few times during the flight, and that Robledo found the dog dead after the plane landed.

The dog's death has gained national attention in the days that followed, and United Airlines immediately took responsibility. The airline said it refunded the airline fares for Robledo, Ceballos and Robledo's infant as well as the $200 fee for Kokito to fly.

I want to help this woman and her daughter. They lost their dog because of an @united flight attendant. My heart is broken. pic.twitter.com/mjXYAhxsAq — MaggieGremminger (@MaggieGrem) March 13, 2018

The airline added that by April, it will begin issuing bright-colored bag tags to travelers flying with pets.

"This visual tag will further help our flight attendants identify pets in-cabin," the airline said.