The wife of an Oxford University professor found dead in Indian-origin colleague Devinder Sivia's house in Oxfordshire defended him, saying the death was 'not murder' and it must have been a 'tragic accident'.

Noted astrophysicist Prof Steven Rawlings was found dead in Sivia's house in Southmoor on Wednesday.

Sivia was taken away by the police from his house in handcuffs and arrested, but was later released on bail until 18 April, without any charge.

Linda Rawlings, wife of the late Rawlings, was distraught at her husband's death, but said he and Sivia, a Mathematics lecturer, were the best of friends, and she did not believe that her husband was murdered.

Linda said: "I do not believe Steve's death is murder... do not believe Devinder should be tarnished. Steve and Devinder were best friends since college and I believe this is a tragic accident".

She added: "Steve is a man of integrity, kindness and a very accessible person. Steve was the love of my life and we have known each other all of these years and he has never changed, even though he has achieved so much and has all these qualities".

Despite initial reports that Rawlings died of a heart attack, a Thames Valley Police spokesman said that a post mortem had proved 'totally inconclusive' and that further tests were being carried out.

Gurbaksha Sivia, father of Devinder Sivia, told the media that Rawlings and his son were 'like brothers'.

He said: "It is a shock, it is a tragedy. It is hard to believe and hard to understand what happened."

Explaining that his son had told him he hoped the matter would be sorted out, he added: "He is shocked himself. He was his best friend. He said nothing of a fight or a falling out. I can't believe they would have fallen out. They have been friends since they were students at Cambridge University. I think for more than 20 years."

Detective Superintendent Rob Mason said: "I would emphasise that the police are investigating all potential circumstances that could have led to his death. We are mindful that ultimately the death may be a matter for a coroner's inquest rather than a criminal court."

Rawlings and Sivia co-authored the book Foundations of Science Mathematics in 1999 and both taught at Oxford for several years.

The Vice-Chancellor of Oxford University, Professor Andrew Hamilton, said: "The entire University community has been profoundly saddened and shocked by the tragic and untimely death of Professor Steve Rawlings.Our thoughts are with his family and friends."

Local resident Duncan Logan, who lives opposite the house of Sivia, said he had known both academics for several years and described them as 'the best of friends'.

He said: "I can't believe what I'm hearing it's like a bolt from the blue. They were the best of friends. They were nice, gentle, well-spoken, polite and hard working people. I am proud to have had both of them as friends. I never heard them row."

He added: "They seemed to respect each other enormously, and talked very highly of each other. I got a text about it today and at first I thought it was Devinder who was dead. I can't imagine Devinder hurting anyone. I've never even heard him raise his voice. He such a gentle person".