(CNN) The executions of three Ohio death row inmates have been delayed as the state continues to develop a new execution-drug protocol, the governor's office said Thursday.

The development of the new protocol was ordered by Gov. Mike DeWine in January, after a US magistrate ruled that the state's current three-drug protocol would cause severe pain and needless suffering, according to a news release.

DeWine said Thursday's reprieves are being issued because it's unlikely the new protocol could be litigated by the scheduled execution dates.

The action brings the number of delayed executions this year to four. In January, DeWine issued a reprieve for Warren Henness based on the ruling.

"Executing [Henness] by Ohio's current three-drug protocol will certainly or very likely cause him severe pain and needless suffering because of the dose of midazolam intended to be used will not render him sufficiently unconscious as to prevent him from suffering the severe pain caused by injection of the paralytic drug or potassium chloride or the severe pain and needless suffering caused by pulmonary edema from the midazolam itself," he said at the time.

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