The woman, 36, is being held for investigation of criminal endangerment and failure to support or care for a dependent person. She has not been charged.
The woman was arrested Monday night after her daughter, who was between 16 and 18 months old, was found not breathing in a car on the Tulalip Reservation.
The girl and her sister, who's 2 1/2, both were rushed to the hospital in need of immediate medical care, according to tribal officials. The younger girl, identified by state social workers Tuesday as Chantel Craig, died.
The older sister remained at Seattle Children's Hospital. Hospital officials on Wednesday said they could not provide additional details about her condition.
Chantel's cause of death remains under investigation. Autopsy results could take weeks.
The tribes have not yet released additional information about the circumstances under which the girls were found.
Tribal investigators are working closely with FBI agents, who often lend assistance with investigations on tribal land, and the Children's Administration branch of the state Department of Social and Health Services.
The woman was booked for offenses under tribal statutes, so documents detailing reasons for her arrest were not available under state records laws.
According to the Tulalip Tribal Codes posted online, a person can be convicted of criminal endangerment if they knowingly engage in conduct "that creates a substantial risk of death or serious bodily injury to another."
An allegation of failure to support or care for a dependent person can involve refusing or neglecting to provide food, shelter or proper care or endangering a child's health, welfare or emotional well-being.
Under tribal law, a conviction of criminal endangerment could lead to up to a year of imprisonment or a $5,000 fine.
Snohomish County prosecutors typically handle serious felony cases involving people living on the reservation, whether or not they are tribal members. As of Wednesday, county prosecutors were not involved in this case.
Rikki King: 425-339-3449; firstname.lastname@example.org
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