The California Department of Corrections is launching an investigation into how former Symbionese Liberation Army member Sara Jane Olson was released from prison at least a year early.
Corrections spokeswoman Terry Thornton says the department's internal affairs division is probing how the mix-up occurred.
Olson was released from prison on Monday after serving half of what was originally calculated to be a 12-year sentence. She was intercepted at Los Angeles International Airport Friday night and returned to prison on Saturday.
In 2001, Olson pleaded guilty to attempted bombings of Los Angeles police cars in the 1970s. Two years later she pleaded guilty to second-degree murder in the 1975 shooting death of a customer during a bank robbery carried out by the SLA near Sacramento.