A girl being treated for abuse at a youth facility in west-central Minnesota was sexually assaulted by an older adult after being allowed to leave without adequate supervision.

Staff at the treatment center, Heartland Girls' Ranch of Benson, allowed the girl to go on two unsupervised trips into the community without properly notifying her county case managers and guardians, according to a state investigative report released Monday.

On the second outing, the girl disappeared for three days and was later found by police in Iowa, with evidence of sexual assault and with bruising on her neck, "as though she had been choked," the report said.

The staff member responsible for communicating with the girl's guardians and case managers in Wright County was cited for seriously endangering the girl's health and has been disqualified from direct contact with vulnerable persons receiving services from state social service agencies.

Heartland Girls' Ranch is a working horse ranch that serves girls ages 12 to 17 who have been victims of sexual exploitation, including human trafficking. Since the assault, Heartland has completed an administrative review and has increased communication between the facility and the residents' treatment team members. The facility's executive director said Monday that they were still reviewing the state report and were preparing a response.

The girl, whose name and age were not released, was admitted to the facility in July and had a history of "acting out on social media and engaging in risky behavior by talking to older [people] online," according to the state report. She also had a history of being sexually abused, as well as running away from home and meeting with strangers, the report said.

Because of her troubled past, the girl's guardians, who were also her county case workers, were supposed to be included in all decisions involving her supervision and care. In September, however, a staff member arranged an unsupervised home visit for the girl without notifying her guardians. During the visit, the girl used a cellphone to contact a much older adult in the community, state investigators found. Staff failed to notify the girl's guardians and did not place any further restrictions on her home visits, state investigators found.

Less than a week later, the girl was allowed to go on another unsupervised home visit, and again, ranch staff failed to notify her guardians. This time, the girl ran away from the home with the older adult, who was later apprehended by police in Iowa when his car ran out of gas, state investigators found. The girl "had been sexually assaulted and had bruising on her neck consistent with being choked," they wrote.

The Wright County case managers told state investigators they would not have approved the second home visit had they known about the girl's cellphone use and contact with the adult during the initial trip. A law enforcement investigation into the assault is ongoing, the state report said.

"There was a cascade of miscommunications here," said Roberta Opheim, state ombudsman for mental health and developmental disabilities. "Each person involved in this girl's treatment appeared to assume that the other was being notified. This was a monumental screw-up."

The assault marks the latest in a string of cases involving the maltreatment of girls at state-licensed children treatment centers across the state. In December 2015, a 25-year-old caregiver at Nexus Glen Lake, a 12-bed facility in Minnetonka, sexually assaulted a 14-year-old girl in her bedroom at the facility, according to a state report. And last year, a 15-year-old girl who ran away from an Itasca County mental health treatment center was sexually abused by an adult counselor who allegedly harbored the girl in her home. The girl was missing for nearly 2 ½ months before Grand Rapids police discovered her in the garage of her counselor.

The state licenses about 120 residential facilities that provide mental health counseling, drug treatment and other services for troubled children and adolescents.

Mental health advocates say children placed in such facilities are particularly vulnerable to maltreatment because they often have long histories of trauma and abuse, and arrive seeking attention and guidance from adult caregivers.