Police said the 21-year-old man was set free Wednesday night.
Ten men are in custody being questioned about possible roles in the blast while six people, including a woman, have been released without being charged.
The suspects still in custody have not been identified or charged.
Police say that the 22-year-old bomber Salman Abedi acted largely alone when he was assembled the device he used to kill 22 people and injure dozens more at an Ariana Grande concert on May 22.