A woman injured with her two daughters in a knife attack in Norwich has been named by police as 23-year-old Victoria Meek.
Officers were called to a flat in Mill Close at about 1230 BST on Tuesday.
Ms Meek and her three-year-old are critical but stable. Her six-year-old is in a stable condition in hospital.
A 28-year-old man, believed to be the father of the younger child, was arrested in Great Yarmouth on Tuesday and is awaiting questioning.
Ms Meek will be questioned by police over the coming days.
She and her elder daughter are at Norfolk and Norwich University Hospital while her younger daughter has been transferred to Addenbrooke's Hospital in Cambridge.
Officers seized what are believed to be the weapons used at the scene and a search of South Beach Parade in Great Yarmouth concluded with no further evidence found.
Police will now conduct a forensic examination of the first-floor flat in Mill Close.
The Independent Police Complaints Commission (IPCC) said Norfolk Police had voluntarily referred the case and asked officials to consider an investigation.
An IPCC spokesman said officials were examining evidence and no decision had yet been made about the launch of an inquiry.