As officials in Oklahoma said they would investigate the botched execution that has drawn worldwide scrutiny, the White House weighed in and said that the execution was not conducted humanely.

“We have a fundamental standard in this country that even when the death penalty is justified, it must be carried out humanely,” Jay Carney, the White House press secretary, said Wednesday during a briefing. “And I think everyone would recognize that this case fell short of that standard.”

The circumstances around the death of convicted killer Clayton Lockett has triggered criticism from across the country and revived the debate over the death penalty and the use of lethal injection.

Lockett had been scheduled for Tuesday night at the Oklahoma State Penitentiary. A gruesome scene unfolded after Lockett was deemed unconscious but then began grimacing, moving his head and trying to get off of the gurney. It was described by witnesses as a horror, leaving several of them shaken and disturbed.

Lockett died of a heart attack 43 minutes after the first injection, with Oklahoma Department of Corrections Director Robert Patton saying at a news conference that the vein line meant to guide the drugs into his body had “exploded.”

This death resulted in the postponement of another execution scheduled for Tuesday night at the same facility and drew criticism from experts, activists and others.

After Lockett began trying to get off the gurney, prison officials closed the blinds, preventing witnesses from seeing him again.

“There was some concern at that time that the drugs were not having that [desired] effect, and the doctor observed the line at that time and determined the line had blown. . . . It was my decision at that time to stop the execution,” Patton said later.

As stunned defense attorneys expressed skepticism and lawyers for the inmate who is scheduled to face execution in two weeks vowed to take legal action, death penalty opponents called for a moratorium on capital punishment in the state.

“In Oklahoma’s haste to conduct a science experiment on two men behind a veil of secrecy, our state has disgraced itself before the nation and world,’’ said Ryan Kiesel, executive director of the American Civil Liberties Union of Oklahoma.

Although the botched execution is expected to trigger further legal challenges to lethal injection, the primary method of execution in the United States, the immediate legal fallout was unclear. The nation’s next scheduled execution is May 13 in Texas, when convicted killer Robert Campbell is slated to die by lethal injection.

That is also the date that Charles Warner, who was scheduled to be executed after Lockett on Tuesday, is now set to be executed. But Oklahoma Gov. Mary Fallin (R), in announcing an independent review into the botched execution and the state’s execution procedures, said that Warner’s execution will be delayed until after the review is completed.

Fallin said Wednesday that she has asked for a review to look into whether the state’s Department of Corrections followed the proper execution protocol with Lockett and figure out recommendations for ways to improve executions. She also said an independent pathologist would determine the precise cause of Lockett’s death.

But Fallin made it clear she still believes Warner should be executed, saying that both Lockett and Warner had their time in court.

“I believe the legal process worked,” she said. “I believe the death penalty is an appropriate response and punishment to those who commit heinous crimes against their fellow men and women. However, I also believe the state needs to be certain of its protocols and procedures for executions and that they work.”

The chain of events in Oklahoma leading up to the botched execution spotlighted the growing opposition to the death penalty nationwide and especially the escalating problems in administering lethal injections. First adopted by Oklahoma in 1977, the method has been fraught in recent years with drug shortages and a host of related problems, including other botched executions.

The U.S. Supreme Court ruled by a 7 to 2 vote in 2008 that the most common method of lethal injection is constitutional. That was a three-drug combination that used an anesthetic, a paralytic drug and a drug that stopped the heart. It was overwhelmingly the primary method of executing condemned prisoners until 2010, according to the Death Penalty Information Center.

But in 2011, Hospira, the sole manufacturer of a key lethal injection drug, sodium thiopental, announced that it would exit the market. That led to a cascade of shortages as states began running out of that and other drugs, in large part because of the European Union’s opposition to the death penalty.

With uncertainty about getting the drugs and legal fights, some states have mulled reviving options such as the firing squad (Wyoming), the gas chamber (Missouri) and the electric chair (Virginia).

Others, such as Ohio, have stuck with legal injection but began using a combination of drugs never before used in the United States. That led to a mishap in the execution of convicted killer Dennis McGuire this year. McGuire, who admitted to raping and murdering a pregnant newlywed named Joy Stewart in 1989, struggled, gasped and choked for several minutes before he was pronounced dead.

Drug shortages are a widespread issue, according to the Government Accountability Office. The GAO recently posted a report noting that the number of drug shortages during a given year has increased since 2007.

Though executions are still continuing in the United States, their numbers have dropped significantly in recent years: Between 1997 and 2005, the nation averaged 71.1 executions each year; between 2006 and 2013, that number dropped to 44.3 executions per year.

More states have recently banned the death penalty, and though a majority of Americans still support the death penalty, that number is dropping, polls show.

In Oklahoma, Lockett and Warner had sued the state for refusing to disclose details about their execution drugs, saying it violated the Constitution’s guarantee against cruel and unusual punishment. They argued that without knowing who manufactures the execution drugs, they had no way of ensuring that the drugs would work as intended.

The case placed Oklahoma’s two highest courts at odds and prompted calls for the impeachment of state Supreme Court justices after the court last week issued a rare stay of execution. The high court later dissolved its stay and dismissed the inmates’ claim that they were entitled to know the source of the lethal drugs, the Associated Press reported.

After Tuesday’s failed execution, Lockett’s attorney David Autry questioned the amount of the sedative, midazolam, that was injected, saying he thought the 100 milligrams called for in the Oklahoma’s execution protocol was “an overdose quantity.” He said he also was skeptical of the department’s determination that Lockett’s vein had failed.

Regarding Warner’s scheduled execution, federal public defender Madeline Cohen, one of his attorneys, told The Washington Post, “Oh, we will be pursuing further action.”

In Virignia, the drug midazolam was approved in February to serve as an alternative first drug in lethal injections. The state said Wednesday that if the drug is used in an execution, it will use 500 milligrams, rather than 100 milligrams.

The Tulsa World’s dramatic account of the events read as follows:

“6:28 p.m. Fifty milligrams of midazolam have been injected into each of Lockett’s arms to start the process, an attempt to sedate him before the second and third drugs are administered to stop the breathing and the heart. Lockett has spent the past several minutes blinking and occasionally pursing his lips.

“6:29 p.m. Lockett’s eyes are closed and his mouth is open slightly.

“6:31 p.m. The doctor checks Lockett’s pupils and places his hand on the inmate’s chest, shaking him slightly. ‘Mr. Lockett is not unconscious,’ Trammell states.

“6:33 p.m. The doctor checks Lockett a second time after a full minute without movement. ‘Mr. Lockett is unconscious,’ Trammell states. It seems like it took longer than expected for this to occur. In past executions I have attended, there has been no notice that the inmate was unconscious, just a pronouncement of death after about eight minutes without much reaction from the inmate.

“6:36 p.m. Lockett kicks his right leg and his head rolls to the side. He mumbles something we can’t understand.

“6:37 p.m. The inmate’s body starts writhing and bucking and it looks like he’s trying to get up. Both arms are strapped down and several straps secure his body to the gurney. He utters another unintelligible statement. Defense Attorney Dean Sanderford is quietly crying in the observation area.

“6:38 p.m. Lockett is grimacing, grunting and lifting his head and shoulders entirely up from the gurney. He begins rolling his head from side to side. He again mumbles something we can’t understand, except for the word ‘man.’ He lifts his head and shoulders off the gurney several times, as if he’s trying to sit up. He appears to be in pain.

“6:39 p.m. The physician walks around to Lockett’s right arm, lifts up the sheet and says something to Trammell. ‘We’re going to lower the blinds temporarily,’ she says. The blinds are lowered and we can’t see what is happening. Reporters exchange shocked glances. Nothing like this has happened at an execution any of us has witnessed since 1990, when the state resumed executions using lethal injection.

“6:40 p.m. A black landline phone rings in the viewing chamber and Patton leaves to take the call, stretching the phone cord out into the hall and closing the door behind him. Though the clock on the wall in the execution chamber is no longer visible, it seems like several minutes pass before Thompson is summoned out to the hallway.

“Approximately 6:50 p.m. Patton comes back to the viewing room and says the execution has been ‘stopped. We’ve had a vein failure in which the chemicals did not make it into the offender. . . . Under my authority, we are issuing a stay for the second execution.’ The announcement is stunning and leaves us wondering what has happened to Lockett.”

Scott Wilson and Rachel Weiner contributed to this report.