Computer errors prompted California prison officials to mistakenly release an estimated 450 inmates with “a high risk for violence” as unsupervised parolees in a program meant to ease overcrowding, according to the state’s inspector general.

More than 1,000 additional prisoners presenting a high risk of committing drug crimes, property crimes and other offenses were also let out, officials said.

No attempt was made to return any of the offenders to state lockups or place them on supervised parole, said inspector general spokeswoman Renee Hansen.