Two more people have been arrested in connection with the suspicious death of a Nottinghamshire women found with head injuries in a flat.
Paramedics found Ms Hill unconscious in the flat
Paramedics found Dawn Hill, 35, unconscious at the property on Farnborough Road, Clifton, at about 1400 BST on Sunday.
She was taken to Nottingham's Queen's Medical Centre where she later died.
The two men arrested on Monday are currently being questioned along with a man and a woman arrested earlier.
A post-mortem examination on Monday found Ms Hill died from a head injury. Police are treating the death as suspicious.
The flat was sealed off while scenes of crime officers carried out forensic examinations.
Police said they were trying to establish Ms Hill's movements in the days leading up to her death and asked for anyone with information about this, or anyone who knew Ms Hill, to contact them.
A police spokesperson said: "We are keeping an open mind as to how Dawn sustained the head injury, which subsequently killed her.
"A serious injury which results in a sudden death will come under suspicion."