A court in the U.S. has agreed to a six-month delay of execution for a death row inmate while an investigation is conducted into last week's botched lethal injection.

The Oklahoma Court of Criminal Appeals on Thursday reset the execution date of inmate Charles Warner to Nov. 13, shortly after the state's top lawyer agreed to the delay while an investigation is conducted into last week's incident.

Attorney General Scott Pruitt and Gov. Mary Fallin have said the state will not carry out any executions until the investigation is complete, which is expected to take at least eight weeks.

Warner was scheduled for execution on the same night last week as Clayton Lockett in what would have been the state's first double execution since 1937. But Lockett's vein collapsed during his lethal injection. It was the first time the state had ever used the sedative midazolam as the first in a three-drug lethal injection protocol.

Lockett writhed on the gurney, gritted his teeth, lifted his head several times and moaned. The curtains that allow witnesses to view the execution were closed about 16 minutes into the lethal injection. The director of the state's prison system, Robert Patton, then called off the execution, but Lockett died of an apparent heart attack, 43 minutes after the start of his execution.

Oklahoma Double Execution

Clayton Lockett, left, and Charles Warner. Lockett's execution by lethal injection was botched April 29, though he later died. Warner's death has been delayed while Oklahoma figures out what went wrong. (Oklahoma Department of Corrections/The Associated Press)

Patton has released a report saying the state didn't have another dose of the drugs available.

States in the U.S. have faced challenges finding execution methods as more companies refuse to supply drugs for executions.

Thirty-two states still have the death penalty, and lethal injection is used in the vast majority of cases, according to the nonprofit Death Penalty Information Center. Thirty-nine people were executed in the U.S. last year, with Texas leading the way with 16 and Oklahoma second with six.

While public support for the death penalty remains strong in the U.S., concerns have been renewed by the execution of Lockett and an incident in January where an Ohio inmate snorted and gasped during the 26 minutes it took him to die.

The investigation into the botched Oklahoma execution will include an autopsy and toxicology tests on Lockett, said Capt. George Brown, a spokesman for the Department of Public Safety, which is conducting the probe.

Oklahoma's governor has said she remains a supporter of the death penalty and believes a majority of Oklahomans also support it.

"Charles Warner had his day in court," Fallin said last week. "He committed a horrible crime."

Warner was convicted of raping and killing his roommate's 11-month-old daughter in 1997. He has maintained his innocence.

Warner's attorneys said in a statement Thursday they were "greatly relieved" the court granted the stay.

"The extreme secrecy surrounding lethal injection that led to Mr. Lockett's agonizing death must be replaced with transparency in order to ensure that executions are legal and humane," attorneys Susanna Gattoni and Seth Day said in a statement.

Lockett and Warner had sued the state for refusing to disclose details about the execution drugs, but the state Supreme Court later dismissed the inmates' claim.