South Carolina mistakenly gave early release to 10 inmates over a two-year period because of errors in calculating their sentences, the state Department of Corrections said this week. Only six have returned to prison, officials said.

Most of the inmates were serving time for drug-related convictions handed down between 2009 and 2017, agency spokeswoman Chrysti Shain told the State newspaper in Columbia. The last of the inmates was released in 2018.

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“SCDC has done a systematic review of its practices and has enhanced the system to make sure these types of errors will not happen again,” Shain told the paper in an email.

“SCDC has done a systematic review of its practices and has enhanced the system to make sure these types of errors will not happen again.” — Chrysti Shain, spokeswoman, South Carolina Department of Corrections

By law, inmates are required to serve at least 85 percent of their sentence. The corrections department caught the error in February after a records review. Prison officials then issued arrest warrants for the inmates who left.

The average length of remaining time on their sentences is two and a half years, Columbia's WIS-TV reported.

“Out of 9,000 to 10,000 inmates who are released each year, 10 were released early,” Republican state Sen. Katrina Shealy, who sits on the Senate Corrections and Penology Committee, told the paper. “It was human error. That’s not an excuse. It’s an explanation.”

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The corrections department did not notify the public about the accidental release, citing that it knew the locations of the inmates and was working with the court system to apprehend them. The victims, however, were notified that the offenders had been let out.