German authorities are investigating how an inmate was allegedly able to rape his wife while she and their children visited him in prison.

Prosecutors in the western city of Koblenz say the 35-year-old suspect allegedly assaulted his wife last week at a prison in the nearby town of Diez, where he was serving a life sentence for murder.

Authorities say the suspect, who was armed with a makeshift knife, was later overpowered by prison guards. It was unclear whether the children were present during the attack.

Chief prosecutor Rolf Wissen declined Tuesday to answer questions about the circumstances of the attack, security arrangements in the prison or the suspect's criminal history, citing the ongoing investigation and privacy rights of the victims.