Authorities in Nebraska have mistakenly freed hundreds of prisoners over several years due to correction officials miscalculating their sentences. Law enforcement is now looking to put dozens of them behind bars again.

All in all, 306 inmates were freed erroneously, a situation first exposed by local media outlet Omaha World-Herald. 257 of them won’t be pursued, on condition that they don’t commit any offenses - because they would have completed their sentences by now. Three others died since they were let go, and five have successfully completed their parole.

On top of that, 567 inmates, who weren’t released, received incorrect sentences, AP reported.

"Obviously, there was a mistake made. The individuals who made those mistakes are going to be held accountable. <…> There's no way this should have occurred," Governor Dave Heineman stated on Friday.

Michael Kenney, who was appointed director of the Department of Correctional Services in September, has already declared that his agency takes full responsibility for the error. He added that his people are "scrambling" to correct the prison sentences, refusing to say if the miscalculation was accidental, or prison officials simply ignored the message from Nebraska’s attorney in the first place.

The mistake, as reported by Omaha World-Herald, is that the Department of Correctional Services failed to observe two Nebraska Supreme Court rulings that indicate the correct way to calculate prison sentences.

Inmates who get a mandatory minimum sentence first have to complete that term before starting to earn so-called “good time” credit, which can cut their remaining term in half.

An example is inmate Marvin Buggs, who was sentenced to 30 years behind bars for manslaughter and wasn’t released.

However, his sentence was still miscalculated.

The mandatory minimum in his case would be 10 years before the start of “good time” – which means he would serve 20 years before becoming eligible for parole. Instead, he was allowed to start his “good time” period right away, and would have been released in 15 years.

An unknown number of prisoners were re-incarcerated on Thursday, and state officials refused to identify them for safety concerns. 20 to 25 arrest warrants were issued in eight counties in Nebraska. Some of the former prisoners would qualify for furlough programs – temporary release from custody – and one is being paroled.

The prisoners have one to four years remaining in their sentences, AP reported, citing Attorney General Jon Bruning.

Many of the inmates are habitual prisoners, and some of them are considered dangerous, Bruning added.