A criminal probe has been launched into a puppy’s death aboard a United Airlines plane after a flight attendant ordered its owners to stow their pet carrier in an overhead bin.

The Harris County District Attorney’s Office in Texas said late Wednesday it is working with the county’s animal cruelty task force to investigate 10-month-old Kokito’s death.

Prosecutors won’t decide if criminal charges are warranted until the probe is completed, officials said in a statement.

The airline is facing a backlash over the French bulldog’s death aboard the Houston-to-New York flight late Monday.

Catalina Robledo, her daughter Sophia Ceballos, 11, and her baby brother were aboard Flight 1284 when a flight attendant told them to place their pet carrier overhead because it was blocking the aisle.

United said the flight attendant didn’t know there was a puppy inside — but the family and other passengers have contradicted the airline’s claims.

Sophia told NBC News that her mom told the flight attendant, “‘It’s a dog! It’s a dog!’ and (the flight attendant) said we have to put it up there.”

“In the end, she says she didn’t know it was a dog, but she actually touched the bag and felt him there. She’s basically lying to us now,” the distraught girl told ABC News.

Other passengers backed up the family’s account on Twitter and Facebook.

United acknowledged Wednesday that the family 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 has declined to identify the crew member.

Meanwhile, the airline said that beginning next month, it will issue brightly colored tags to passengers traveling with pets so flight attendants can easily recognize the animals, ABC News reported.

“To prevent this from happening again, by April we will issue bright colored bag tags to customers traveling with in-cabin pets,” United said in a statement.

The heart-breaking story prompted the group People for the Ethical Treatment of Animals to call for the flight attendant to be fired and charged with animal cruelty, ABC News reported.

Sen. John Kennedy (R-Louisiana) also said he sent a letter to United president Scott Kirby, “demanding an immediate explanation for the number of animals who have died recently in United Airlines’ care.”

“This pattern of animal deaths and injuries is simply inexcusable,” the letter read. “For many people, pets are members of the family. They should not be treated like insignificant cargo. Frankly, they shouldn’t be placed in the cargo hold much less an overhead bin.”

Kennedy said he plans to file a bill Thursday that would prohibit airlines from placing pets in overhead compartments.

“Violators will face significant fines. Pets are family,” he wrote.

The US Department of Transportation is also looking into the circumstances surrounding Kokito’s death, an agency spokesman said Wednesday.

The department “is in contact with the US Department of Agriculture, the agency that enforces the Animal Welfare Act and handles complaints about alleged animal mistreatment,” the spokesman said.

The Federal Aviation Administration is also looking into the incident and will “review the airline’s investigation,” FAA spokesman Greg Martin said.

Last year, 18 animals died while being transported on United — three-fourths of all animal deaths on US 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 about every 4,500 animals transported last year.

United 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,” United spokesman Charles Hobart said.

He 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.

United touts its pet-shipping program, called PetSafe, but some are skeptical of its safety.

“I think United tries to make a business out of pet transport with this program, but (airline) ramp workers are not veterinarians,” said Brian Kelly, CEO of The Points Guy, a travel website that first reported Kokito’s story.

According to reports filed with the government, in most cases of animal death or injury last year, United took no corrective action.

Some pets were deemed to have died of natural causes, others from heart problems or gastric dilation, a condition associated with eating too much.

One dog died of heat stroke, and another animal escaped while being handed back to its owner and was hit by a vehicle.

With Post wires