Oklahoma's January execution of convicted murderer and rapist Charles Warner is now under fire and being investigated after his exhumed remains tested positive for the drug potassium acetate, which is not authorized for use in the state's lethal injections protocol.

The same questionable drug was what halted the execution of Richard Glossip, as reported by HNGN, as just moments before his lethal injection, the execution team opened the box of drugs sent to it and realized the wrong drug had been sent.

The controversy surrounds data reports that list that a drug used to kill Warner was potassium chloride, the approved drug as part of the three drug protocol for execution. Instead, Warner tested positive for potassium acetate. Data records are maintained to ensure all legalities are correct when an execution takes place, but now doubt surrounds their accuracy.

Investigations are underway into the errors and Warner's execution, according to The Huffington Post.

Potassium acetate is at the center of the current halting of all Oklahoma executions, as previously reported by HNGN, when an alleged mix-up by the drug supplier to the Oklahoma execution team caused the states attorney's office to file with Oklahoma Court of Criminal Appeals asking to halt all scheduled executions indefinitely.

Since new concrete evidence shows the same drug was used in January of this year to execute Warner, questions have arisen as to the validity of a mix-up.

While some are claiming the drugs potassium chloride and potassium acetate are interchangeable, experts on pharmaceuticals and chemistry said on Thursday that there are differences, according to CNS News. Whereas potassium chloride is more quickly absorbed by the body, potassium acetate takes longer and more of it is needed to mimic what the potassium chloride does.

With the records indicating the same amount was used in Warner's autopsy report, experts said it might not have worked as quickly as the drug for which it was substituted.

"The state's disclosure that it used potassium acetate instead of potassium chloride during the execution of Charles Warner yet again raises serious questions about the ability of the Oklahoma Department of Corrections to carry out executions," said Glossip's attorney Dale Baich, according to NPR. "The execution logs for Charles Warner say that he was administered potassium chloride, but now the state says potassium acetate was used. We will explore this in detail through the discovery process in the federal litigation."