The evening shift was assigned to clean an agitated mixing vessel. The supervisor asked the lead operator to complete the ¿Lock out.¿ The lead operator tagged and locked out the motor starter in the Motor Control Center, verified the motor would not start by pressing the Start button and put a lock and ¿Danger¿Do Not Operate¿ tag on the Start-Stop station near the vessel. The supervisor then issued the Confined Space Entry permit and two workers entered the vessel and cleaned it for the rest of the shift.The oncoming day shift needed to reissue the Confined Space Entry permit. When they tried the Start button on the Start-Stop station, the agitator started! The agitator motor was NOTlocked out