OMAHA, Neb. — The American Civil Liberties Union sued the Nebraska’s prison system Friday, accusing it of violating state public records laws by refusing to identify its suppliers of lethal injection drugs.

The Nebraska Department of Correctional Services denied a Nov. 10 public records request by The Associated Press, and the Omaha World-Herald reported Tuesday that its request also was denied.

The department argues that the records are protected by attorney-client privilege and that the supplier is part of its “execution team,” whose identities are confidential.

The ACLU disputes both arguments and is seeking the information’s release and attorney fees.

“This lawsuit lays out Nebraska’s shady history of backroom deals and attempts to circumvent federal law to obtain lethal injection drugs,” ACLU of Nebraska Executive Director Danielle Conrad said in a written statement.

The department notified inmate Jose Sandoval on Nov. 9 that it intends to execute him using four drugs. An execution date hasn’t been scheduled. Sandoval, 38, was one of three men sentenced to death on five counts of first-degree murder for the September 2002 deaths of five people in a botched bank robbery in Norfolk, a city of 24,000 about 110 miles northwest of Omaha.

With the notification to Sandoval, the department announced it intends to use the sedative diazepam, commonly known as Valium; the powerful synthetic opioid fentanyl citrate; the paralytic cisatracurium; and potassium chloride to induce death. A department spokeswoman, Dawn-Renee Smith, said then that the system had access to all four drugs and that all were purchased in the U.S., but she declined to say how the drugs were obtained or who provided them.

Smith declined to comment on the lawsuit Friday, saying the department doesn’t publicly discuss pending litigation.

Nebraska’s death penalty has been roiled by controversy in recent years. In 2013, the state’s batch of sodium thiopental — then required for Nebraska lethal injections — expired. State officials failed several times to replace the drug, including in early 2015 when it paid $54,000 for the drug to a dealer based in India but never received it because the federal government blocked the shipment over questions about the drug’s legality.

The Legislature abolished the state’s death penalty in May 2015 over Gov. Pete Ricketts’ veto, but capital punishment was reinstated last year by Nebraska voters in a referendum funded, in part, by $300,000 of Ricketts’ own money.

Nebraska hasn’t executed an inmate since 1997, when it used the electric chair, and has never carried one out with lethal injection drugs.

“We understand that Nebraskans of goodwill do hold differing opinions about the death penalty, but we shouldn’t allow the Department of Corrections to disregard the law and the Nebraska tradition of open government for pure political reasons,” Conrad said.