Fallout from the death of a French bulldog named Kokito continued for United Airlines on Thursday, as the airline explained how the dog had come to die in an overhead compartment and two United States senators introduced a bill to stop such a thing from ever happening again.

United’s admission followed an uproar over the Monday death of Kokito, who was placed in the overhead bin shortly before a flight left Houston for New York.

Maggie Schmerin, a spokeswoman for United, said that the airline had spoken to the family, the flight crew and passengers who had been seated nearby. The flight attendant who placed the carrier in the overhead bin said she had not heard the owner tell her that the dog was in the carrier, Ms. Schmerin said. A witness and the owner said the dog had been barking before takeoff.

“As we stated, we take full responsibility and are deeply sorry for this tragic accident,” Ms. Schmerin said. “We remain in contact with the family to express our condolences and offer support.”