In 2005, a dead baby was found at an airport. Her mother had just been arrested.

The dead baby girl was found in a garbage can in a ladies' room at Phoenix's main airport on October 10, 2005. The newborn, wrapped in newspapers and a towel, was placed in a plastic bag at a Marriott Hotel, police said. .

Detectives immediately began investigating the death of the child, who became known as Baby Skylar. A medical examiner determined two days after the baby was found that she had been suffocated and had been the victim of a homicide. But leads in the case eventually dried up and the investigation lay dormant for years.

On Tuesday, more than 18 years after the gruesome discovery at Phoenix Sky Harbor International Airport's Terminal 4, authorities announced at a news conference that they had identified and arrested the baby's mother, Annie Anderson, 51, of Washington state. would be charged with first-degree murder in the child's death.

Ms. Anderson remained in custody in Washington on Tuesday and awaiting extradition to Maricopa County, Ariz., Phoenix police Lt. James Hester said at the meeting. news conference.

One of the few and first clues police had was the plastic bag in which the baby's body was found. That prompted investigators to investigate Marriott hotels in the Phoenix area, Lt. Hester said. But those and other clues turned out to be unsuccessful.

Then in 2019, Phoenix police worked with the FBI to use genetic genealogy, an emerging tool in solving cold cases, to investigate the Baby Skylar mystery, Lt. Hester said.

Dan Horan, a supervisory special agent with the FBI field office in Phoenix, said at the news conference that the two agencies used a process known as investigative genealogy, which uses existing DNA evidence from an unknown person and attempts to find relatives based on publicly available genealogical databases.

By doing that, the two agencies were able to find a possible relative of Baby Skylar. That family member, who was not identified by authorities, agreed to share a sample of their DNA with authorities for a single use, Officer Horan said.

In January 2022, investigators traveled to Washington state, where they executed a search warrant and interviewed Ms. Anderson, authorities said. Lt. Hester said Ms. Anderson confirmed she was the mother of Baby Skylar and told police what happened.

“We have a dead child, we have an identified mother and we have her statement,” Lt. Hester said.

Authorities declined to share details of Ms. Anderson's story. Through the investigation, authorities learned that Ms. Anderson was visiting Phoenix on business for a real estate boot camp in October 2005, and that the child, Lt. Hester, was most likely not born at the airport.

It was not immediately clear Tuesday whether Ms. Anderson had an attorney.

During the investigation, authorities were also able to identify the baby's father, and it was determined that he had no “criminal culpability,” Lt. Hester said. Authorities have not named the father.

Sergeant Rob Scherer of the Phoenix Police Department said Tuesday that the investigation has “affected many people at many different levels of this department and beyond” and will “remain in the minds of many officers involved.”