There is currently no evidence to suggest anyone else was involved in the death of Russian oligarch Boris Berezovsky, police have said.
The 67-year-old businessman was found dead at his Berkshire home on Saturday by a bodyguard, and specialist officers in chemical, biological, radiological and nuclear substances examined the property today before giving the all clear.
Detective Chief Inspector Kevin Brown, of Thames Valley Police, said: "It would be wrong to speculate on the cause of death until the post mortem has been carried out. We do not have any evidence at this stage to suggest third party involvement."
Berezovsky, who last year lost a multibillion-pound High Court battle with Chelsea FC owner Roman Abramovich, was reportedly found dead in his bathroom after taking his own life.
On leaving the property, the paramedic who declared him dead at the scene had their radiation detector triggered, prompting the CBRN (chemical, biological, radiological and nuclear) experts to examine Berezovsky's country pile, police said. But on Sunday morning they confirmed the home at Titness Park, Mill Lane, Ascot, was safe to work in.
The paramedic's detector, a personal electronic dosimeter (PED), is a health and safety device used routinely by emergency services. "An employee" of Berezovsky, believed to be the bodyguard, had called for the ambulance shortly after 3pm on Saturday after forcing open a bathroom door and finding the oligarch dead on the floor.
The employee had not not seen Berezovsky since 10.30pm on Friday night and had become concerned for his welfare, according to police.
Scenes of crime officers are currently carrying out a full forensic examination of the scene and earlier today a forensic investigation unit vehicle could be seen passing through police cordons around Berezovsky's estate. A Home Office post-mortem will be carried out.
Det Ch Insp Brown continued to describe the death as "unexplained". He said: "We are at the early stages of the investigation and we are retaining an open mind as we progress.
"The investigation team are building a picture of the last days of Mr Berezovsky's life, speaking to close friends and family to gain a better understanding of his state of mind. We are acutely aware of the level of interest into his death and are focused on conducting a thorough investigation as we would with any unexplained death."