(CNN) -- Exiled Russian oligarch Boris Berezovsky's death is "consistent with hanging" with no sign of a violent struggle, British investigators announced late Monday.
The 67-year-old Berezovsky was found dead at a country estate south of London over the weekend, triggering speculation about the fate of a onetime tycoon known for his opposition to Russian President Vladimir Putin.
"The results of the post-mortem examination, carried out by a Home Office pathologist, have found the cause of death is consistent with hanging," Thames Valley police reported. "The pathologist has found nothing to indicate a violent struggle."
Investigators are still waiting for toxicology test results, which could take several weeks, the statement said. And the house in Ascot will remain under guard while investigators continue to probe his death, police added.
He was found in the locked bathroom of a guest suite, police confirmed. Police scouring the scene Sunday said they had not found any sign of "third-party involvement," a detective said.
Speculation about Berezovsky's cause of death ran the gamut from suicide to heart attack with some pointing to his declining fortune as a possible clue. He is believed to have been in serious financial difficulties after running up huge legal fees in recent years, including what was reportedly Britain's biggest-ever divorce settlement and a losing lawsuit against a former friend and ally, Chelsea football club owner Roman Abramovich.
A close family friend, speaking to CNN on condition of anonymity, said that Berezovsky was found dead by a bodyguard -- a former member of the Israeli spy agency Mossad, as Berezovsky's bodyguards all were. He normally had three, but only one was working at the time he died, the friend said.
The home where Berezovsky died is owned by his ex-wife Galina, the friend said, but Berezovsky had been staying there for a month because few people knew how to reach him there. He believed his houses were bugged had repeatedly re-written his will over the last few years; in addition, the source said, he had discussed the importance of returning to Russia and was contemplating having his body repatriated to his homeland.
He was not on medication, as far as the source was aware.
Another source characterized Berezovsky's finances as "an immediate liquidity squeeze, but long-term, he had assets."
Over the weekend, close associates had denied that Berezovsky may have committed suicide, Russia's state-owned RIA Novosti news agency reported. The agency said a family friend told Russian media that Berezovsky had suffered a heart attack.
The colorful Berezovsky had been a Moscow math professor and systems analyst before the Soviet Union broke apart in 1991. In the freewheeling era that followed, he made a fortune selling cars and parlayed those riches into political influence by buying into Russian media outlets.
He supported Boris Yeltsin, Russia's first post-Soviet president, and was an early backer of Putin. But after winning his Kremlin office in 2000, Putin's government began trying to collect on tax claims against "oligarchs" like Berezovsky.
Berezovsky fled Russian and began agitating against Putin from Britain, calling for a coup to oust the Russian president. In 2003, as Russia was seeking his return, Berezovsky was granted political asylum by British authorities after they realized he was wanted on political grounds, not criminal ones, according to published reports at the time.
The case strained relations between Moscow and London. Berezovsky was convicted of fraud and tax evasion in absentia by a Russian court in 2007.
Berezovsky also blamed the Kremlin for the death of former Russian spy Alexander Litvinenko, who was poisoned by radioactive material in London. For years, Berezovsky bankrolled the effort of Litvinenko's widow to push for an inquest into her husband's death.
In a deathbed statement, Litvinenko blamed Putin, an accusation the Kremlin strongly denied.
Moscow is ready to consider burying him in Russia, if it receives such a request, Russian media said, quoting presidential spokesman Dmitry Peskov.
CNN's Nina dos Santos, Susannah Palk, Per Nyberg, Tom Watkins and Chelsea J. Carter contributed to this report.