It has been discovered that computer errors led to the mistaken release of hundreds of high-risk California prisoners.

Some 450 high-risk prisoners and over 1,000 state inmates with various offenses were freed as unsupervised parolees under a program created in January last year to ease overcrowding.

An investigation by the state's inspector general revealed that inmates were placed on non-revocable parole, according to the Los Angeles Times. This means the prisoners are not required to report to parole officers and would be ordered back to prison only if they committed a crime.

The program was intended for inmates at low risk for re-offending, so that parole agents can focus on more higher-risk parolees.

According to the inspector general, the computer system used in the program doesn't access an inmate's disciplinary record and lacks conviction files for nearly half of California's 16.4 million arrest records, according to LA Times.

The report Confirms my worst fears, said State Sen. Ted Lieu (D-Torrance) who requested the investigation.

Lieu told the Times, if the state can't properly identify which inmates qualify for an unsupervised parole program, how can the public have confidence they can release 33,000 felons safely?

According to inspector general spokeswoman Renee Hansen, there was neither an attempt to return any of the mistakenly-released offenders nor have them placed on supervised parole.

The shocking revelation comes just days after the U.S. Supreme Court ordered California to release some 33,000-46,000 prisoners.