A man has been arrested on suspicion of murdering a young child found in a critically ill condition.
Police officers and paramedics were called to Frosterley Drive, near Haughton Road in Darlington, at 09:00 GMT on Friday morning.
The one-year-old was was taken to the Royal Victoria Infirmary in Newcastle but died on Saturday afternoon.
A woman in her 40s has been arrested on suspicion of causing or allowing serious injury to a child.
