A Prison Service spokesman said ex-Manchester City youth player Courtney Meppen-Walter was released "in error" and added that such incidents are taken "extremely seriously".
Police have been informed after a prisoner was released in error on Monday July 1 to ensure he is promptly returned to custody.
Releases in error are very rare and we take any incident extremely seriously. An investigation will take place into the circumstances that led to this release.
Meppen-Walter wept in court when he was jailed at Manchester Crown Court on February 28.
More top news
A woman hit by police gunfire during a counter-terrorism operation has been arrested after being released from hospital.
Police have been granted extra time to question a man who is being held on suspicion of planning a terror attack.
The man opened fire at the house, shattering the front door and window.