Detective Inspector Mark Bissell of Thames Valley Police said there were no signs of a struggle, but that the involvement of a third party "cannot be completely eliminated as tests remain outstanding."
Investigators have not specified the nature of the ligature—a cord or other material used for binding—that was found around the neck of the 67-year-old oligarch.
Berezovsky, a one-time Kremlin powerbroker-turned-critic of Russian President Vladimir Putin, lived in self-imposed exile in Britain.
Bissell said Berezovsky was last seen alive at 9:05 p.m. on Friday. His body was found Saturday by a member of his staff at 3:20 p.m. at his mansion in Ascot, 25 miles (40 kilometers) west of London.
Police are still searching the property and toxicology tests are being conducted on Berezovsky's body.
Several wealthy Russians have died suddenly in Britain in recent years—most notoriously Berezovsky's friend Alexander Litivinenko, who died in 2006 of poisoning after ingesting the radioactive isotope polonium-210. Britain has accused two Kremlin-linked Russians in the killing of the former KGB agent, who had fled to Britain.
Speculation has swirled about possible foul play in Berezovsky's death.
A mathematician-turned-Mercedes dealer, Berezovsky built up his wealth during Russia's chaotic privatization of state assets in the 1990s following the 1991 breakup of the Soviet Union.
Berezovsky helped build up Putin's power base but fell out of favor and was charged in Russia with fraud and embezzlement.
A U.K. coroner's inquest—held to determine the facts in cases of violent or unexplained deaths—opened with a brief hearing Thursday at Windsor's Guildhall, then was adjourned to a later date.
Officials said Berezovsky had legally changed his name to Platon Elenin in 2003 and would be identified by that name at the inquest.