ARLINGTON — A Mill Creek woman allegedly left her baby alone at night in an unlocked car while she gambled at a casino Sept. 8.

The mother, 27, was arrested at Angel of the Winds Casino. She was held on $7,500 bail Monday for investigation of criminal mistreatment and abandoning a dependent person, both misdemeanors.

Surveillance footage showed the mother walking into the casino around 12:45 a.m. She reportedly told police she had called someone to care for the baby while she was inside, a probable cause affidavit says. No one showed up.

The mother gambled for at least 17 minutes.

People in the parking lot heard a crying baby. They reported that she appeared to be in distress.

The 1-year-old wasn’t strapped into her car seat. The car’s back door was unlocked. Her diaper and clothes were soaked with urine, the affidavit says.

Stillaguamish Tribal Police later found a box underneath the baby’s car seat containing an uncapped syringe, drug paraphernalia and a debit card in the mother’s name, court papers say.

An officer went inside the casino to find the mother. Another stayed behind with the baby.

The officers asked the woman to change the girl’s urine-soaked diaper. The mother said she didn’t have spare diapers with her. She also tried several times to feed the baby formula from a bottle, which had gone rancid and begun to grow mold.

She told police her daughter had been fussy because she was sick and hadn’t seen a doctor yet.

Police said it would be best for the baby to stay with other family members.

The woman was arrested and remained in custody Monday at the Snohomish County Jail in Everett.

Her parents petitioned for custody of a toddler in 2015, citing their daughter’s drug history and negligence of parental duties. That child’s father also petitioned for custody that same year.