(CNN) — The Louisiana department of corrections is keeping more than a quarter of inmates behind bars past their scheduled release date, the US Justice Department said in a report Wednesday.

According to the Justice Department, between January and April 2022 alone, nearly 27 percent of those released from LDOC custody — nearly 4,100 people — were held past their release dates.

Of those held beyond their release dates, 24 percent were held for at least 90 extra days.

"Our investigation uncovered evidence of systemic violations by the Louisiana Department of Public Safety and Corrections that have resulted in the routine confinement of people far beyond the dates when they are legally entitled to be released," said Assistant Attorney General Kristen Clarke, who heads DOJ's Civil Rights Division.

The DOJ began the investigation in 2020, saying the state's over-detention issues had stretched on for years with no action taken. The report cited a decade of "systemic deficiencies" in the state.

"These violations are in large part caused and exacerbated by systemic deficiencies in LDOC's policies and procedures related to the receipt of sentencing documents, computation of an incarcerated individuals' release dates, and employee training," the department said in a letter that accompanied the report.

The Justice Department said it could sue the state if it doesn't correct these issues in a matter of weeks, the letter continued, but prefers to "resolve this matter through a more cooperative approach."

"The Constitution guarantees that people incarcerated in jails and prisons may not be detained beyond their release dates, and it is the fundamental duty of the State to ensure that all people in its custody are released on time," Clarke said.

Ken Pastorick, an LDOC spokesperson, said in a statement to CNN that the department is reviewing the report and that it "will continue to work with DOJ throughout this process."

Mercedes Montagnes, the executive director of Promise of Justice Initiative, a nonprofit in New Orleans that supports and advocates for the rights of people in the justice system, told CNN that the report's findings are "egregious" and "frankly worse than we imagined."

"This is what the Justice Department is here for," Montagnes said. "We've been shouting, we've been screaming, we've been crying from every rooftop ... for advocates like us this is validating. It's energizing to know that the full power of the federal government is going to come down here and hold people responsible."

This story has been updated with additional details.

The-CNN-Wire
™ & © 2023 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.