A fourth person was arrested by detectives today investigating the murder of a 40-year-old.

Two men and a woman arrested after the discovery of the man's body in Luther Court, off Speedwell Street, on Sunday have been released on police bail.

The victim, who had not been formally identified this morning, was found after police were called to flats in the city centre street at 1.10pm for another incident, police spokesman Vicky Evans said.

It was believed at first the man had been beaten to death. However, a post mortem examination proved inconclusive and further tests to determine what killed him were being carried out, she said.

The fourth person, a man, was arrested this morning on suspicion of murder and questioned by detectives.

Neighbours told yesterday of previously hearing arguments inside the flat.

News of the man's death was only released by police yesterday afternoon.

Detectives arrested a 40-year-old woman and a 38-year-old man in Oxford at about 6.30pm on Sunday. A 44-year-old man was arrested afterwards.

A 31-year-old man, who has lived in a flat opposite for the past two years but did not want to be named, told the Oxford Mail he had often heard the flat's occupant arguing.

He said: "I could hear him fighting. It often got quite loud.

"My wife is eight months' pregnant, so this has been quite worrying."

Stephen Broadway, 36, who lives in a different block of flats in Luther Court, added: "I came back from my usual walk along the river on Sunday afternoon and I saw a number of police cars and vans, and some paramedics."

In September, police were called to investigate the unexpected death of Michael Alistair Calvey, who also lived in Luther Court. Police later decided not to class the incident as a murder inquiry.