A man aged in his 20s who was arrested in relation to an alleged assault in prison has been released without charge.
The alleged assault took place in the Midlands Prison in Portlaoise on December 6.
He was arrested on Tuesday morning by officers from the Serious Crime Unit and was held at a Garda station before being released later on Tuesday.
Gardai said he was returned to prison.
They are continuing to investigate all the circumstances around the incident.
Four men in their 20s and 30s arrested on Friday in connection with the alleged attack were later released without charge and returned to the prison.
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