Lindsay M. Kronberger died from probable heart problems, dehydration and opiate withdrawal, according to the Snohomish County Medical Examiner's Office.
The Snohomish County Sheriff's Office, which runs the jail, also has wrapped up its death investigation, spokeswoman Shari Ireton said.
In addition, the sheriff's office conducted a morbidity review, a new kind of assessment for inmate deaths that started after a federal analysis of jail operations last year.
Kronberger was the ninth inmate to die at the jail since 2010. A number of changes have been made and are under way to address problems identified in the analysis.
Ireton on Wednesday said she could not discuss the findings of the morbidity review under medical privacy laws.
Kronberger had been in the jail from Jan. 3 until Jan. 6 after a domestic-violence incident. She was released Jan. 6 and booked again early Jan. 7 for violating an order related to the same case.
She was being kept in the jail's medical unit when she was found unresponsive at 1 a.m. Jan. 13.
Kronberger was described in an online memorial as happy, outgoing and spiritual. A funeral was held in Everett in January. Her family has asked for privacy.
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