ANN ARBOR, Mich. >> Michigan’s prison system is the target of a class-action lawsuit alleging that guards and other workers failed to prevent the sexual assault of male teen inmates who were locked up with adults.

Inmates under 18 were forced to engage in sex acts with adult prisoners and staff, according to the lawsuit, with some abuse “open and obvious.” The Corrections Department disputes the allegations, and state attorneys have argued that employees shouldn’t be held liable.

But after more than a year of litigation, the inmates have some important victories. Judge Carol Kuhnke agreed to make the case a class-action and declared that Michigan’s civil rights protections apply. More than 200 potential victims have contacted the lawyers, who also plan to hold meetings at prisons.

The case in Washtenaw County court is led by a legal team that negotiated a $100 million settlement in 2009 for hundreds of female prisoners who said they were assaulted or harassed by male guards.

Corrections Department officials “implemented this intermixing policy knowing that they were creating hell for these younger people inside these adult prisons. Their eyes were wide open,” attorney Michael Pitt said in court last fall.

“It’s a case of gross negligence, deliberate indifference, intentional misconduct — you name it,” he said.

The attorney general’s office has fought back at many turns. It has repeatedly appealed Kuhnke’s key rulings, even challenging whether Washtenaw County is the appropriate place for the case, but hasn’t prevailed so far. By December, the cost of providing prison documents to lawyers and meeting other requests was nearly $500,000 and growing.

“We are confident the assertions made in the lawsuit are false,” Corrections Department spokesman Chris Gautz told The Associated Press.

In court, the state has argued that officials can’t always be held responsible.

“There are inherent risks of being incarcerated, whether someone is under 18 years old or they are over 18 years old. … Prisons are not where you want to spend your time,” Assistant Attorney General Mark Donnelly told the judge. “Just because someone is in our custody and they get injured, it does not mean we are liable for that injury.”

Teens can be charged as adults in Michigan, especially for violent crimes. The lawsuit involves allegations of sexual assault at prisons throughout the state, from Marquette in the Upper Peninsula to Gus Harrison in southern Michigan, mostly before the Corrections Department assigned all males under 18 to a prison in Lapeer. That transition began in 2012.

Inmates, typically 16 or 17, were “forced to shower, eat, recreate and work with adult prisoners without adequate supervision to ensure their safety,” attorney Deborah LaBelle said.

The U.S. Bureau of Justice Statistics has reported that about 2 percent of teens — male and female — were victims of sexual misconduct by other inmates in U.S. jails and prisons in 2011-12. The number was higher for assaults by staff.

After the lawsuit was filed, the attorney general’s office said it interviewed roughly 200 young inmates and found no widespread abuse or mistreatment. Lawyers on the other side protested when they learned about the meetings, saying the inmates could have felt coerced into giving answers that would keep them out of trouble.

The case still has a long way to go. More appeals of the judge’s rulings are pending, and talks aimed at a possible settlement have been scheduled for later this year.

“We’re eager to begin the process of bringing these issues to trial,” LaBelle said.