The American Civil Liberties Union on Monday asked the U.S. Drug Enforcement Administration to investigate whether the state of Nebraska broke the law when buying four drugs to use in executions.

Nebraska ACLU Legal director Amy Miller wrote in a letter to the DEA that the state Department of Correctional Services appeared to have imported the opioid fentanyl, a drug for which it lacked a license, and misled suppliers about the intended use of all four drugs.

In November, Nebraska officials said they had purchased a new supply of lethal injection drugs and would move to have execution dates set for two death-row inmates.

The state had been without a method to execute people for several years due to a shortage of the required drugs in its old execution protocol and political wrangling over the death penalty.

 The state penitentiary has two permits from the DEA — one allowing it to import specific controlled substances and another allowing it to dispense prescription medications to inmates as part of medical treatment.

The prison is not licensed to import the opioid fentanyl, one of four drugs that are part of Nebraska’s execution protocol, Miller wrote in the letter, which the ACLU posted online. She added that it appears that the state may not have informed suppliers that the drug was to be used for executions.

“Prisoners who are to be executed by lethal injection are not being diagnosed or treated,” Miller wrote. “Nor are they being provided any other form of medical care.”

Corrections spokeswoman Dawn Renee Smith said the drugs were purchased legally in the United States.

“The ACLU’s letter to the DEA is another attempt to stop lethal injection and contains inflammatory language clearly intended to discredit the department,” she said in an email on Monday.

Nebraska ACLU Executive Director Danielle Conrad said via email that the purchase of the drugs is“in service of the state’s attempts to keep its machinery of death churning,” calling it a“cover-up.”

 Nebraska’s supply of sodium thiopental, part of the state’s prior execution protocol, expired in December 2013, and the state was unable to buy more due to difficulties in procuring the drug.

The Nebraska Legislature in 2015 repealed the state’s death penalty and then overrode Governor Pete Ricketts’ veto of the measure. However, death penalty proponents succeeded in placing the issue on the ballot and voters rescinded the repeal in 2016.

The state then adopted the new execution protocol, which calls for different drugs.

Reporting by Kevin O'Hanlon; Editing by Patrick Enright and Leslie Adler