Hennepin County has launched an unusually wide-ranging internal review into its handling of a case of extreme child maltreatment at a south Minneapolis home, where twin girls with developmental disabilities allegedly endured years of horrific abuse by their parents.

The county hopes to determine why child protection workers and other authorities did not detect years of abuse and remove the two girls from a home that prosecutors have called a "house of horrors." The twin girls, now 21, have described being repeatedly raped, beaten with bats and chained for days at a time without food.

"We need to know what worked, what didn't work, and how do we learn from this ... so ideally we don't have a repeat," said Hennepin County Deputy Administrator Jennifer DeCubellis, who oversees the county's child protection division.

The review comes nearly a month after the arrest of the girls' father, and it will be unusually broad in scope. County officials intend to scrutinize every interaction between the family and social service agencies, schools, police and the courts.

Systemwide reviews of this kind have been conducted by Hennepin County in just a handful of child maltreatment cases, which underscores the severity of the breakdown and the county's determination to pinpoint its root causes. Reviews of this depth are typically confined to cases with child fatalities or near fatalities resulting from maltreatment, officials said. In 2015, for instance, a state mortality review panel issued a detailed report, with numerous recommendations, following the highly publicized murder of 4-year-old Eric Dean after 15 ignored reports of child abuse.

"This is breaking new ground," said Rich Gehrman, executive director of Safe Passage for Children of Minnesota, a watchdog group for child welfare. "It speaks to how seriously they are taking this case. ... Everyone is wondering how the abuse could have gone on so long without some action being taken."

The Minnesota Department of Human Services, which oversees the state's child protection system, will keep tabs on the county's review, a spokeswoman said.

The case has aroused alarm among child welfare advocates and residents of the south Minneapolis community where the girls lived and attended school.

According to court documents, Jerry Lee Curry, 52, kept his developmentally delayed daughters chained to a bedroom door for days at a time; beat and raped them; and allegedly allowed drug dealers to have sex with them in exchange for crack cocaine. The chains were so tight around one girl's ankles that she developed gangrene and had to undergo surgery, court records show.

Clinicians who examined the twins and their multiple scars concluded they had been subjected to abuse that was "clinically diagnostic of torture," court records show.

The abuse went largely undiscovered for years until one of the twins ran away last May and described her ordeal to workers at a shelter. When police finally entered the house, they discovered what they called a "sex chamber," with pornographic videos and a heavy wooden paddle wrapped in tape. It was later determined that Curry fathered two children with one of the twin girls.

Court records indicate that as far back as 2013, Hennepin County child protection workers knew of possible abuse in the home. One of the children reported that Curry struck her in the back of the head with his fist, and then banged a sibling's head on the countertop. A third, younger child in the home reported being punched in the face multiple times, court records show.

Even so, the county did not open a formal maltreatment investigation. Instead, the case was put on what is called a "family assessment" track, a less-confrontational approach intended to keep families together. The county offered the family support services, but the children's mother, Shelia Machelle Wilson, 48, declined, according to court records.

At a community forum last week, a number of neighbors said they repeatedly reported problems at the family's small blue house on the 4200 block of 17th Av. S. They questioned why authorities did not act sooner to rescue the siblings. Records show that police visited the house more than 50 times for multiple reports of domestic violence and missing children.

"There were multiple agencies that really dropped the ball," said Minneapolis City Council Vice President Andrea Jenkins, who spoke at the meeting. "Either these agencies did not believe the reports [of abuse], or they really didn't rise to the level of creating some safety nets for these young women. Either way, there has to be some sort of analysis to identify the weak links in the system."

The case has already taken a toll on workers in Hennepin County's child protection division, which has been deluged with accusatory calls and e-mails since reports of the abuse surfaced last month.

"It's so easy to blame," DeCubellis said. "The amount of hate mail that we've got, and that our staff continue to get, is astronomical."

Still, county officials emphasized that their review is not intended to assign blame to any individual or agency. Instead, county authorities will meet with social workers and others who interacted with the family at critical points, and talk through their decisions, DeCubellis said.

The effort is part of a new, collaborative approach to reviewing extreme incidents of child maltreatment, rolled out since last summer by the Department of Human Services in response to a sharp rise in child fatalities from maltreatment. Statewide, about 1,500 county workers have been trained on using the new model to review child fatalities and near fatalities.

The goal of the approach is to examine how the system failed without creating an "atmosphere of fear" among those involved in the case, DeCubellis said.

Dr. Mark Hudson, a child abuse specialist and medical director of the Midwest Children's Resource Center in Minneapolis, said the case is a good one for the new form of review. "It has the ability to get at the people doing the work and finding out what was really going on, and what was driving the decisions that were made."

Added DeCubellis: "We want to understand, could we have done something different earlier? It's not about blaming any one person or entity. It's really about, how can we learn from this?"

Chris Serres • 612-673-4308 Twitter: @chrisserres