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DENVER — A teenage girl confessed to shoving a small rock down her newborn baby’s throat, the Denver Police Department said Wednesday.

Authorities said the infant was killed shortly after birth in early September and pronounced dead at Children’s Hospital Colorado in Aurora, the Denver Medical Examiner’s Office said.

The baby, named Amekah, was found behind a home in Green Valley Ranch, according to a probable cause affidavit. An autopsy revealed the cause of death was suffocation.

RELATED: Probable cause affidavit

The mom has been identified as 16-year-old Alaya Dotson by the Denver District Attorney’s Office. She told police she didn’t know she was pregnant, according to court papers.

Authorities said Dotson took her newborn to the backyard after a surprise delivery. She told detectives the baby fell out of her arms after her mom walked outside and startled her.

Police said Dotson admitted to picking up a rock and pushing it down the baby’s throat. Police said Dotson admitted her role in the baby’s death after being read her Miranda rights.

Dotson is facing a first-degree murder charge, according to the district attorney’s office and will be tried as an adult.

She has a preliminary court hearing scheduled for Jan. 12.