A 51-year-old man from St Albans, who had been arrested as part of an investigation into the death of a ten-month-old baby, has been released from police custody.
Hertfordshire Constabulary say no further action will be taken against him.
A 37-year-old man from Hatfield who was also arrested as part of the investigation remains in police custody.
Investigations into the cause of death of the boy, who died at the Lister Hospital on the evening of June 1, continue.
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