A 10-year-old girl with Type 1 diabetes died after slipping into a coma while on a road trip with her family over the summer, authorities said. Now, her mother has been charged with manslaughter for allegedly delaying seeking life-saving medical care for the child, who was dead by the time she got to a hospital, according to the charging document.

Police in Washington state said they began investigating the death after the child’s mother brought her to a hospital in Tacoma in July. The girl, from Kirkland, is believed to have died from prolonged diabetic ketoacidosis, or DKA, police said.

Following a monthslong, “extensive” investigation, the mother was arrested earlier this month for first-degree manslaughter and remains booked on $1 million bail while awaiting trial, the Kirkland Police Department said Friday.

Prosecutors allege in the charging document that her mother “failed to provide life-saving care for her child, despite substantial education and training on the life-threatening risks of prolonged periods of high blood sugar when a child has Type 1 Diabetes.”

The girl, her siblings, her mother and her mother’s boyfriend had left home on July 17 for a family road trip to the Oregon-California border, according to the charging document. The day before the trip, the girl’s insulin pump began displaying “high” blood glucose levels, according to the document. Prior to leaving on the trip, she had also been vomiting, which is a symptom of diabetic ketoacidosis, the probable cause filing stated.

They traveled to Northern California before turning around for an approximately nine-hour drive back to bring the girl — whose name has not been released by police and is referred to in court filings by initials — to the hospital in Tacoma, according to the charging document.

On the morning of July 18, the girl’s mother allegedly texted her own mother, an employee at Mary Bridge Children’s Hospital in Tacoma, “I’m bring [the girl] in she is DKA we was on way to California but she was taking her pump out,” according to the charging document.

By the time they got to the hospital later that afternoon, the girl had likely been dead for several hours, according to the charging document.

“Rigor mortis had set in, and her body was stiff, indicating [the girl] had been dead for several hours in the back seat of the car, alongside her older sister and younger brother,” the charging document stated.

On the approximately 714-mile drive to Tacoma, her mother passed more than two dozen hospitals, and cell phone records indicated she never called 911, according to the charging document.

When interviewed by police, the mother allegedly said she did not call 911 or stop at another hospital because, per the parent plan she has with the girl’s father, she was not allowed to take her out of state. The mother is separated from the child’s father, and at the time of the incident, the girl was in her mother’s custody and care, police said.

“She stated she did not know what the consequences would be if [the girl’s]’s father was notified that she took [the girl] out of the state without permission,” the probable cause filing stated.

The mother also allegedly told police that her daughter forgot to bring her ketone test kit on the trip, according to the charging document. Elevated ketones are a sign of diabetic ketoacidosis, which is a “medical emergency that needs to be treated immediately,” according to the Centers for Disease Control and Prevention.

Since being diagnosed with Type 1 diabetes in 2018, the girl had been hospitalized for diabetic ketoacidosis multiple times, according to the charging document. Following her most recent hospitalization in May, the mother received retraining from medical professionals on how to use the insulin pump and the life-threatening nature of diabetic ketoacidosis “given the concerns about the defendant’s prior mismanagement of the victim’s condition,” the charging document stated.

Her mother — identified in court filings as Lloydina McAllister, 42 — has pleaded not guilty, according to online court records. Her trial is scheduled to start in late December. ABC News has reached out to her attorneys for comment but has not yet received a response.

“This was a complex and emotionally challenging investigation,” Kirkland Police Chief Mike St. Jean said in a statement. “The collaboration between our detectives, medical professionals, and prosecutors was essential in bringing clarity to what happened. We remain committed to protecting our community’s most vulnerable residents, especially children who cannot advocate for themselves.”