A lawsuit filed by the American Civil Liberties Union contends that the Nobles County Sheriff’s Office has illegally detained immigrants at the request of federal officials.

Even though Sheriff Kent Wilkening doesn’t have the authority to enforce federal immigration law, the suit says, he has held people for “days, weeks and even months” after they’ve posted bond, completed their sentence or otherwise resolved their criminal cases.

The class-action suit filed in Nobles County names four plaintiffs, three of whom were still in detention as of Friday, said ACLU attorney Ian Bratlie.

“They don’t have any legal reason to hold people under our state Constitution,” said Bratlie. “All four should have been released.”

The suit alleges there are many more who have been and will be detained unless a court grants relief.

Wilkening was not available for comment Friday, nor was Bill Hutton, the head of the Minnesota Sheriffs’ Association.

The plaintiffs in the ACLU suit include Worthington resident Rodrigo Esparza, a green card holder and lawful permanent U.S. resident. He was arrested four months ago on allegations of receiving stolen property and sentenced to time served in early August. Wilkening has not released him from detention, however, instead holding him for immigration authorities.

In other cases, the plaintiffs allege that they’ve been subjected to false imprisonment after paying a bond or after having their case dismissed by a judge.

It’s the second time the ACLU has taken legal action against immigration detentions in Nobles County, on the Iowa border in southwestern Minnesota.

In its 2014 suit against the Sheriff’s Office, the ACLU won a settlement for Jose Lopez-Orellana after his family paid bail money only to see him remain on an ICE hold for 10 more days.

The issue of ICE detentions has shadowed local law enforcement in recent years. In 2014, Hennepin County Sheriff Rich Stanek’s office cited legal challenges in saying it would no longer honor ICE requests to hold inmates for up to 48 hours.

The Nobles County jail is one of four jails in Minnesota housing immigration detainees. The others are in Sherburne, Freeborn and Carver counties. Ramsey County stopped taking ICE detainees last year.

Bratlie, the ACLU attorney, said it’s unknown how many people are now being held in custody in Minnesota at the request of immigration authorities.

The ACLU says a data practices act request earlier this year found that some 270 people in Nobles County had been subject to an ICE hold in the first three months of this year.