(CNN) - Oklahoma state officials announced Thursday that the state will resume executions by lethal injection, having found a "reliable supply."
The state hasn't executed a death row inmate since January 2015, when Charles Warner was put to death by lethal injection. Another inmate, Richard Glossip, was scheduled to be executed in September of that year but then-Gov. Mary Fallin called for it to be postponed.
A ban on executions was put in place several days later as the state investigated whether the wrong drug was mistakenly used and a grand jury reviewed the execution protocol.
The state will now use a revised version of the protocol that includes recommendations from the 2016 multicounty grand jury.
"I believe that capital punishment is appropriate for the most heinous of crimes and it is our duty as state officials to obey the laws of the state of Oklahoma by carrying out this somber task," Gov. Kevin Stitt said at a news conference
The three drugs that will continue to be used are midazolam, vecuronium bromide and potassium chloride, according to Oklahoma Attorney General Mike Hunter.
"There are sufficient drugs to begin the process of scheduling executions," he said.
The review of the process came in the wake of the 2014 botched execution of Clayton Lockett. Having been sentenced to death for the 1999 shooting of Stephanie Nieman, Lockett was scheduled to die by a three-drug lethal injection cocktail in April 2014 at the Oklahoma State Penitentiary in McAlester. Thirty-three minutes after the administration of the first drug began, the execution was halted.
"The doctor checked the IV and reported the blood vein had collapsed, and the drugs had either absorbed into tissue, leaked out or both," according to a previously released timeline. Lockett died of a heart attack 43 minutes after the execution began.
After Warner's execution the following January, officials learned their drug supplier had sent the Department of Corrections potassium acetate instead of potassium chloride, Fallin said at the time.
She said: "Until we have complete confidence in the system, we will delay any further executions."
Hunter, the attorney general, said Thursday that carrying out a death sentence is his most profound responsibility.
"The additions that we've made to the protocol simply add more checks and balances, more safeguards, to the system to ensure that what happened in the past won't happen again," he said.
The updated protocol includes verifying execution drugs at each step and more training for execution teams.
He said he will pursue working to gain the ability to use a gas, nitrogen hypoxia, for executions. A 2015 law says the state cannot use nitrogen hypoxia unless the three-drug combination is not available.
There are 47 people sentenced to death in Oklahoma, 26 of whom have exhausted their appeals, according to the attorney general..
Hunter said the state's Department of Corrections cannot set execution dates for people who have no more appeals until 150 days have passed.
He said state law prohibits him from releasing information about the drug supplier or suppliers.