The bodies of a woman and two children have been found at a flat in Liverpool that John Lennon lived in.
Police were called to a ground floor flat on Falkner Street, near Toxteth, Liverpool shortly before 19:30 BST on Tuesday.
A man, 30, was detained on suspicion of murder before being taken to hospital after falling ill.
Merseyside Police believe the incident was domestic in nature. It said it was not looking for anyone else.
A police spokesman said tests were being carried out on a substance found at the scene.
The arrested man was taken to hospital before being discharged and taken to a police station for questioning.
The force added a post-mortem examination will be carried out to establish the causes of death.
Neighbours said the property in the Georgian Quarter was regularly visited by Beatles fans on tours of the city.
The flat was once owned by the band's manager, Brian Epstein, and Lennon lived there with his first wife Cynthia shortly after they married in 1962.