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Thames Valley Police said that further tests, including toxicology examinations, will be carried out. The force did not specify whether the 67-year-old businessman hanged himself.
A forensic examination of Berezovsky's home will continue for several days, police added.
Once one of Russia's richest men and a Kremlin powerbroker, Berezovsky fled to Britain in 2001 and claimed political asylum in the country after a bitter falling out with Russian President Vladimir Putin. He had since been a vocal critic of the Kremlin.
Berezovsky's body was found by an employee on the bathroom floor at his upscale England home on Saturday. The employee called an ambulance after he forced open the bathroom door, which was locked from the inside. Police said the employee was the only person in the house when Berezovsky's body was discovered.
The businessman had survived several assassination attempts, including a car bomb in 1994 that killed his driver.
He amassed his fortune in the 1990s during the chaotic privatization of the Soviet Union's state-run economy, building up an empire that included a car dealership, media interests and oil assets.
But in recent years his fortunes declined with numerous expensive court cases. Last year Berezovsky lost a huge legal battle against former business partner and fellow Russian tycoon Roman Abramovich, which left him with legal bills estimated to cost tens of millions of pounds.
