A federal judge in Alabama ordered the state on Thursday to stop executions until the U.S. Supreme Court reviews a drug used in lethal injections that is allegedly leading to a prolonged and painful death for prisoners subjected to the drug cocktail, Reuters reported, citing the Birmingham News. Alabama’s first execution of 2015 was reportedly scheduled for Thursday. 

The Supreme Court agreed to review the drug after a lawsuit was filed by three death row inmates in Oklahoma over the use of lethal injection, claiming that it violated the U.S. Constitution's ban on cruel and unusual punishment. According to reports, Oklahoma’s lethal injection protocol is similar to Alabama’s, which has not carried out an execution since 2013, due to a shortage of drugs used in the lethal injection. Alabama will now hold off on all executions until the court rules on the lawsuit filed by the Oklahoma prisoners.

“The state has conceded that the best course of action is to stay decisions on the lethal-injection cases across the board until (the Oklahoma case) is decided,” U.S. District Judge Keith Watkins reportedly said.

Thursday’s order came in response to a complaint filed by condemned murderer Tommy Arthur challenging Alabama's method of lethal injection as unconstitutional. Watkins reportedly said that six other Alabama death row inmates have filed similar lawsuits, and that he has ordered a stay of execution in five of the cases, the Birmingham News reported.

The three-drug process used by Oklahoma prison officials has been under scrutiny since April 2014 following the death of convicted murderer Clayton Lockett from a heart attack, minutes after a doctor halted his execution after the procedure went awry. The botched execution attempt, which some witnesses compared to watching a horror movie, raised questions about the drug cocktail and lethal injection procedure used for death penalty by the state and others.

"His body started to twitch, he mumbled something I couldn't understand," Dean Sanderford, Lockett’s attorney, reportedly said, at the time. "The convulsing got worse, it looked like his whole upper body was trying to lift off the gurney. For a minute, there was chaos."