London: Boris Berezovsky, a self-exiled Russian tycoon and a staunch critic of President Vladimir Putin, has been found dead in mysterious circumstances in southeast England.
Berezovsky, 67, was reportedly found dead in his bathroom yesterday and police are currently treating his death as "unexplained".
Police said experts searching his house in Berkshire found no chemical, radiological or biological materials.
Officials with expertise in environments contaminated with chemical, biological, radiological and nuclear (CBRN) material had been searching the house of Berezovsky, onetime Kremlin kingmaker.
"CBRN trained officers have concluded their examination of a property in Mill Lane, Ascot following the unexplained death of a 67-year-old man, believed to be Russian national Boris Berezovsky, and have given the scene the all clear," Thames Valley police said in a statement today.
The police force`s Scenes of Crimes Officers are now carrying out a "full and thorough" investigation at the property to determine the circumstances surrounding the death.
"I am pleased to say the CBRN officers found nothing of concern in the property and we are now progressing the investigation as normal," said Superintendent Simon Bowden, the local police area commander.
Speculation over Berezovsky`s cause of death ran the gamut from suicide to heart attack.
"Initial suggestions that Berezovsky may have committed suicide were quickly quashed by his close associates," Russia`s RIA Novosti news agency reported.
The agency said a family friend told Russian media that Berezovsky had suffered a heart attack.
Berezovsky emigrated to the UK in 2000 after falling out with Putin.
The business tycoon amassed a fortune in the 1990s after the privatisation of state assets following the collapse of Soviet Communism. He survived numerous assassination attempts, including a bomb that decapitated his chauffeur.
In 2003, he won political asylum to stay in Britain on the grounds that his life would be in danger in Russia.
The tycoon`s wealth is thought to have considerably diminished in recent years, leaving him struggling to pay debts in the wake of costly court cases.
In 2011, Berezovsky reportedly lost more than 100 million pounds in a divorce settlement. And, last year, he lost 3 billion pounds damages claim against Chelsea Football Club owner Roman Abramovich.
He had blamed Kremlin for the death of Alexander Litvinenko, a former Russian spy who was poisoned by radioactive material.
Berezovsky was a close friend of Litvinenko, a Russian emigre and former KGB officer Alexander Litvinenko, who died in 2006 after he was poisoned with the radioactive material polonium-210 while drinking tea at a London meeting.
Lord Bell, a PR executive who had acted as Berezovsky`s spokesperson and was also a good friend, described his state of mind as "extremely depressed".
Russian media described Berezovsky`s death as "the end of an era".