A woman in her 30s was arrested earlier this week after a man was seriously injured in North Lynn.
Emergency crews were called to St Edmundsbury Road following reports someone was believed to have been fatally injured.
A man in his 30s was found at the scene with serious injuries to his head and torso.
Police have said no other victims were involved in the incident, which happened at around 6.40pm on Monday, and the man was taken to the Queen Elizabeth Hospital in King’s Lynn for treatment.
A woman was arrested at the scene on suspicion of assault and taken to King’s Lynn Police Investigation Centre.
The following day a spokesman for Norfolk Police said: “The incident is believed to have happened within the areas of Coulton Close/Newlands Avenue/St Edmundsbury Road, and a police seal is in place at Coulton Close while officers carry out further enquiries.”
Police are keen to hear from anyone who holds CCTV or dash cam footage from the areas mentioned between 5pm and 7.30pm on Monday, or from those who witnessed suspicious activity during these times.
Anyone with information is asked to contact Swaffham CID on 101, quoting crime reference number 36/2453/22.