OKLAHOMA CITY (AP) — Oklahoma has missed a self-imposed deadline to finish creating a new execution protocol involving nitrogen gas, and it's unclear when executions will resume in the state.

Attorney General Mike Hunter and Department of Corrections Director Joe Allbaugh announced in March that they intended to switch to nitrogen hypoxia for executions in Oklahoma. The announcement came after the state had trouble obtaining lethal injection drugs amid opposition from drugmakers to having their products used in executions.

Officials had hoped to have the new plan drafted by July. But Hunter's...