A 40-year-old man has been detained under the Mental Health Act following the death of a woman.
Cambridgeshire Police said officers were sent to a property on Norris Road in St Ives at 07:30 GMT on Monday after reports of a "sudden death".
The man was arrested on suspicion of murder.
Detectives were not looking for anyone else in connection with the incident and a cordon was put in place in the area.
Det Insp Dale Mepstead said: "Our thoughts go out to this woman's family and loved ones at this difficult time."
No-one else was injured and a post-mortem examination was due to be carried out, police said.
Anyone with any information was asked to get in touch.