Mystery surrounds the death of a 74-year-old man at his Bradford home.
Toxicology tests are underway in a bid to establish exactly how the pensioner died.
A man was initially arrested on suspicion of murder but he has since been released on bail.
Paramedics were alerted just after 9.30am on Saturday after the man's son found him collapsed at his home in Sticker Lane, Laisterdyke. He was pronounced dead at the scene.
Detectives were called in because of concerns over minor injuries the man had sustained.
A post-mortem examination failed to establish the cause of death and further toxicology and histology tests will now be carried out.
A West Yorkshire Police spokesman confirmed yesterday that officers were called to a address in Sticker Lane, Bradford, at 9.37am on Saturday after paramedics found the body of a 74-year-old man in the property.
The spokesman said: "Concerns were raised by medical staff about slight injuries to the man's upper body.
"A 45-year-old man was later arrested on suspicion of murder."
The spokesman added: "The post-mortem examination has proved inconclusive. The 45-year-old man has since been released on bail pending further inquiries."
It is now believed the death is not suspicious.
Witnesses told how uniformed police guarded the premises while scenes of crime officers examined the scene on Saturday.
Yesterday, neighbours living around the semi-detached house said they had not heard or seen any commotion before police arrived on the scene on Saturday. Many also said they didn't know the people living in the house, other than to say hello, although one man said a father and son lived in the property.
He added that the dad was not very mobile and sometimes used a wheelchair.
The senior investigating officer in the case is Detective Chief Inspector Steve Snow, of West Yorkshire Police's Protective Services (Crime) department.
Det Chief Insp Snow said: "The man was found dead at his home. He had some superficial injuries which caused us to follow a particular course of action. Further tests will now take place to establish the cause of death. The man who was arrested has now been released on bail."
Anyone with any information about the death is asked to contact Protective Services (Crime), via 101.
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