Ariel Castro was being held in protective custody in isolation from other inmates at the Correctional Reception Center in Orient, Ohio when he was found dead last night.
According to media reports in the US, he was being checked on every 30 minutes.
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The operation to recover the unexploded bomb near the Houses of Parliament let to disruption in central London overnight.
Southern parts of England and Wales will see sunny skies after a frosty start.
A police spokesman said the incident in the Bourke Street Mall on Friday was not related to terrorism.