More than 200 men and women were sexually abused as children while in custody at juvenile detention centers in Illinois, according to lawsuits filed on Monday, the latest in a string of complaints alleging decades of systemic child sex abuse.

Three lawsuits filed on Monday detail abuse from 1996 to 2021, including rape, forced oral sex and beatings by corrections officers, nurses, kitchen staff, chaplains and others.

“The State of Illinois has caused and permitted a culture of sexual abuse to flourish unabated in its Illinois Youth Center facilities,” one lawsuit said, adding that Illinois had “overwhelmingly failed to investigate complaints, report abusive staff, and protect youth inmates”.

Overall, 667 people have alleged they were sexually abused as children at youth facilities run by the state and Cook county in lawsuits filed since May.

They are part of a wave of complaints with disturbing allegations at juvenile facilities across the US, including in Pennsylvania, Maryland, New Jersey, New Hampshire, California and New York. Few cases have gone to trial or resulted in settlements; arrests have been infrequent.

Illinois stands out for the magnitude of its problem.

“Of all the states in which we’ve been litigating, we are seeing some of the worst and highest numbers of cases of staff perpetrating sexual abuse compared to anywhere in the country,” said Jerome Block, a New York-based attorney whose office brought the lawsuits in Illinois and several other states.

Monday’s complaints, based on the accounts of 272 people, name several repeat offenders. A handful have been convicted of sex crimes but not stemming from the accusations in the lawsuits. At least one employee accused in a lawsuit filed on Monday still works for the state, according to state records.

The lawsuit with the largest number of plaintiffs, 222 men and women who are mostly Illinois residents, details abuse at nine state-run youth detention centers, of which five have since closed. The accounts documented in the complaint’s more than 400 pages are hauntingly similar.

Many said their abusers threatened them with beatings, solitary confinement, transfers to harsher facilities and longer sentences if they reported the abuse. Others were given extra food, cigarettes and rewards such as the chance to play video games if they kept quiet.

Most abusers are identified only as the survivors remembered them, including by physical descriptions, first names or nicknames.

The lawsuit covering state-run facilities names the state and the Illinois department of corrections and department of juvenile justice as defendants. State agency officials did not immediately return requests for comment on Monday.

The lawsuit, filed in the Illinois court of claims, seeks damages of roughly $2m per plaintiff, the most allowed under law.

Another lawsuit, focusing on a troubled Chicago youth detention facility, was filed in Cook county court and names the county.

It covers allegations from 50 men and women who were in custody at the Juvenile Temporary Detention Center. It said many instances of abuse took place during unlawful strip searches.

Children were as young as 11 when they were abused, according to the lawsuit, which seeks damages of $100,000 per plaintiff. Some of the 50 plaintiffs are seeking more damages in a third lawsuit filed on Monday in the Illinois court of claims.