Staff error resulted in 152 federal inmates being freed after their correct release dates between 2009 and 2014, including three who spent more than an extra year behind bars, according to a report released Tuesday by the Justice Department watchdog.  

The inspector general report counted a total of 4,340 Bureau of Prisons inmates who received "untimely" releases during those years.  

Of those cases, 157 were classified by the BOP as due to "staff errors," such as employees who misapplied credit for time served, the report stated.

Just five of those mistakes led to early releases; in the rest, inmates served more time than they should have, with one prisoner serving roughly three additional years.  

"Late releases from prison deprive inmates of their liberty, while early releases can put communities at risk if the inmates are dangerous," the report states.  

The overwhelming majority of "untimely" releases were for reasons that the BOP said were beyond its control, such as sentences that were changed by court orders after the inmate had begun serving them. In some instances, an inmate had already served more time than the new sentence imposed.  

The inspector general report called on the Justice Department and the BOP to improve training and to establish a process for notifying prosecutors and court officials about untimely releases.   The inspector general's review followed news reports in 2014 after an inmate over being held for 13 months beyond his correct release date. That suit was ultimately settled for $175,000.