More than 3,200 prisoners in the US have been released early due to a software glitch.
The error miscalculated the sentence reductions that prisoners in Washington state had received for good behavior.
It was introduced in 2002 as part of an updated version that followed the Court's decision on the application of good conduct credits.
State officials said many inmates released early would have to return to prison to finish their sentences.
"This problem has been allowed to continue for 13 years and it is deeply disappointing to me, completely unacceptable and, frankly, outrageous," Washington Governor Jay Inslee said at a press conference.
The Washington Department of Corrections (DOC) added that it became aware of the problem in 2012 when a victim's family found out that the perpetrator had been released too early.
Despite this, the faulty software was not fixed until a new IT boss was appointed at DOC, who realised how serious the problem had become.
The director then notified senior officials at the DOC and the governor's office.
Analysis of the errors showed that, on average, prisoners whose sentences were incorrectly calculated were released 49 days early. One prisoner had his sentence reduced by 600 days. It is not known whether any offenders committed crimes after their early release .
Local police are now helping to round up those who still have to serve time in prison. Five people have already returned to their cells.
Mr. Inslee said he had ordered the DOC to fix the software as quickly as possible.
An updated version that implements the correct formula for calculating cuts is expected to be in place by January 7. Until then, the DOC has been ordered not to release any inmates without manually verifying that they should be released.
An independent investigation has also been launched to discover how the error went uncorrected for so long.
