Arizona plans to execute prisoners with the same deadly gas used by the Nazis at Auschwitz, documents show

The Guardian obtained documents showing Arizona's purchases of ingredients for hydrogen cyanide.

The documents also showed the state's refurbishment of a gas chamber.

Hydrogen cyanide was used by the Nazis in Auschwitz and other extermination camps.

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The state of Arizona has plans to use hydrogen cyanide, the deadly gas used by the Nazis at Auschwitz and other extermination camps, to kill inmates on death row, documents obtained by The Guardian's Ed Pilkington showed.

The Arizona Department of Corrections spent more than $2,000 in procuring the ingredients for the gas, The Guardian reported, citing the partially redacted documents.

The ingredients purchased include a solid brick of potassium cyanide, sodium hydroxide pellets, and sulfuric acid, the documents showed.

Cyanide is lethal in that it prevents the body from using oxygen. It was used in both World Wars — by French and Austrian troops in World War I, and by Nazi Germany in World War II, said a 2014 fact sheet by the Johns Hopkins Center for Health Security. The trade name for hydrogen cyanide is Zyklon B.

The department has also refurbished a gas chamber in Florence, Arizona, that was built in 1949 but had not been used for 22 years, The Guardian reported.

The chamber was tested for "operational functionality" and "air tightness" last August, and in December, following a refurbishment, officials "verbally indicated that the vessel is operationally ready."

The documents published by The Guardian also included instructions on how to operate the gas chamber.

In a statement to Insider, the Arizona Department of Corrections, Rehabilitation and Reentry said it was "prepared to perform its legal obligation and commence the execution process as part of the legally imposed sentence, regardless of method selected."

The last person to be executed in the gas chamber in Arizona was the German national Walter LaGrand, an armed robber put to death in 1999. A witness account published in the Tucson Citizen said it took LaGrand 18 minutes to die. The witness account said he "began coughing violently — three or four loud hacks — and then, in what appeared to be his last moments of consciousness, he made a gagging sound before falling forward at about 9:15 p.m."

Arizona law says anyone who was sentenced to death before November 1992 can choose whether to be executed by lethal injection or lethal gas.

But there have been no executions for seven years following the botched death penalty of the murderer Joseph Wood in 2014, The Guardian reported. Wood took two hours to die following 15 injections as he lay gasping and gulping on a gurney.

In April, The Guardian reported that the state had spent $1.5 million on execution drugs, including 1,000 1-gram vials of pentobarbital sodium salt.

Pentobarbital is a sedative often used in vet clinics or physician-assisted suicides in Europe, The New York Times reported in 2011. It's also used in Arizona in 5-gram doses to cause a fatal overdose, The Guardian said.