“I can tell you, he was snoring,” said Stephanie Grisham, a spokeswoman for the Arizona attorney general who was a witness. “There was zero gasping or snorting, and that’s just the truth. He was asleep.”

Image Joseph R. Wood III Credit... Arizona Department of Corrections, via Associated Press

Mr. Wood was executed for the 1989 murders of his estranged girlfriend, Debra Dietz, and her father, Eugene Dietz.

Some family members of the victims said they were not concerned about the execution method, The Associated Press said.

“This man conducted a horrific murder and you guys are going, ‘Let’s worry about the drugs,’ ” Richard Brown, brother-in-law of Debra Dietz, told The A.P. “Why didn’t they give him a bullet? Why didn’t we give him Drano?”

Gov. Jan Brewer of Arizona said that she was concerned about the length of time the execution took.

“While justice was carried out today, I directed the Department of Corrections to conduct a full review of the process,” she said. “One thing is certain, however: Inmate Wood died in a lawful manner, and by eyewitness and medical accounts he did not suffer. This is in stark comparison to the gruesome, vicious suffering that he inflicted on his two victims — and the lifetime of suffering he has caused their family.”

But state officials offered no immediate explanation for why the procedure dragged out so long.

The events in Florence, Ariz., on Wednesday bore eerie parallels to a botched execution in Oklahoma in April, which also followed unsuccessful appeals to force the state to reveal more details about lethal drugs. In Oklahoma, Clayton D. Lockett visibly gasped and writhed on a gurney for several minutes, then later died of what state officials said was heart failure.

In that case, preliminary indications are that the catheter was improperly placed, spilling the execution drugs into Mr. Lockett’s tissue rather than into his veins so that he was only partly sedated before receiving a partial dose of a painful heart-stopping drug.