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 16ft python that would have been "capable of attacking a person" has been found dead in a canal sparking a police investigation.
A six-year-old boy was shot in the stomach by his brother, aged five, in the third child shooting in just four days in Texas.
Social media users have been sharing their amended versions of the incredible pictures.