As many as 3,200 felons may have been released early over 13 years – about 3 percent of the number of offenders released. All those released had enhancements for special sentences, state officials said. (A sentence enhancement gives harsher punishments to felons.)

“I have a lot of questions about how this happened,” Inslee said, noting the public would also have questions, and saying that an external, independent investigation would find what went wrong.

Department of Corrections Secretary Dan Pacholke, who oversaw the agency when some of the offenders were released incorrectly, called the situation and “unforgiveable error.”

“I’ve apologized to the governor personally on behalf of the Department of Corrections for this 13-year error,” Pacholke said. “I want to offer the same apology to the public.”

The State Department of Corrections first learned of the problem in 2012, but it continued.

>>Associated Press: 5 prisoners released early are back in prison

How did this happen?

A fix was repeatedly delayed “for reasons still being investigated,” according to a statement from the Governor’s office.

The problem dates back to July 2002. The state Supreme Court ruling requires DOC to apply credits for an inmate’s good behavior during time in county jail to his or her overall state prison sentences.

Before the ruling, that “good behavior” credit in county jail did not roll over to count in prison sentence reduction.

Inslee said a computer program included inaccurate sentencing that over-credited the good time reduction. Five of the offenders have already been contacted and returned to prison, Pacholke said.

When a new DOC chief information officer was hired, department leadership and Inslee were notified. A new software system is expected to be in place by January 7.

DOC is halting the release of all offenders within the group of offenders affected by the enhancement-sequencing error -- until a hand calculation is done to ensure the offender is being released on the correct date.

Officials are working to locate offenders released from prison prior to their earned release date -- to ensure they fulfill their sentences as required by law.

Most of the offenders released early will be given day-for-day credit for their time in the community.

Depending on how much time they have left to serve, the offenders will go to work release or back to prison.

What are the key dates?

July 2002: State Supreme Court required DOC to apply credits for good behavior in county jails to state prison sentences.

2012: DOC realizes there was a problem with computer "sequencing" that determined when an offender would be released. The fix is repeatedly delayed "for reasons that will be investigated," Inslee said.

Dec. 22, 2015: Inslee acknowledges as many as 3,200 offenders may have been released early over 13 years. Department of Corrections Secretary Dan Pacholke apologizes, calling the mistake that was on part of his watch an "unforgiveable error."

Jan. 7, 2016: Insee said a broader software fix is expected in place by this date. The governor orders a halt to all releases until a check can be done by hand.

>> Read Associated Press updates.