(CNN) -- The Supreme Court cleared the way late Tuesday for the execution of convicted killer Jeffrey Landrigan in Arizona, with a majority of justices deciding to vacate a federal judge's order that had temporarily stopped the execution scheduled for earlier in the day.
In a 5-4 decision, the court overturned two lower court rulings that had stopped the execution.
Earlier Tuesday, the 9th U.S. Circuit Court of Appeals had sided with U.S. District Court Judge Roslyn Silver, who blocked Jeffrey Landrigan's execution 18 hours before it was set to happen at noon MT Tuesday (2 p.m ET).
Landrigan's attorneys filed a civil rights complaint last Thursday alleging the planned execution violated his constitutional rights to be free from cruel and unusual punishment and to due process. On Monday, Silver issued the temporary stay after concluding that the state did not provide Landrigan's side enough information to make its case sufficiently about the safety and legality of substances that would have been used to kill him.
But the U.S. Supreme Court ruling vacated the lower court order, saying "there is no evidence in the record to suggest that the drug obtained from a foreign source is unsafe."
Judge Silver wrote that she "was left to speculate" that the drug was harmful, but in a statement the Supreme Court -- citing a different 1993 ruling -- concluded in a one-page order that sentiment should not equate to the fact it was "sure or likely to cause serious illness or needless suffering."
"There was no showing that the drug was unlawfully obtained, nor was there an offer of proof to that effect," the Supreme Court ruling said.
The decision to vacate the order was supported by Chief Justice John Roberts and Justices Samuel Alito, Anthony Kennedy, Antonin Scalia and Clarence Thomas. Justices Stephen Breyer, Ruth Bader Ginsburg, Elena Kagan and Sonia Sotomayor sided with Silver and would not have vacated the ruling.
No further appeals were expected at the high court, and the execution could proceed in the coming hours.
In 1989, Landrigan escaped from an Oklahoma prison, where he was serving time for second-degree murder. He was convicted of strangling Chester Dean Dyer in Arizona a year later during an armed burglary, and a trial judge sentenced him to death.
The high court appeal is Brewer v. Landrigan (10A416).
CNN's Bill Mears contributed to this report.