The death of Russian business tycoon Boris Berezovsky was "consistent with hanging", say police based on the autopsy report.
Investigators have ruled out any suggestion of violence in the death of the 67-year-old, whose body was found in his Berkshire mansion by an employee.
More tests, including toxicology and histology, are to follow the post-mortem. Further investigations will be carried out over several weeks, said office.
"The results of the post-mortem examination, carried out by a Home Office pathologist, have found the cause of death is consistent with hanging. The pathologist has found nothing to indicate a violent struggle," said the Thames Valley Police.
Pathologists from the Home Office are dealing with the case due to its sensitive nature.
The police had earlier said there were no signs of "third party" involvement in the death.
"A cordon will remain in place until this work has been completed, to protect the scene. While this important investigative work continues we are unable to comment on any items found within the property," detective chief inspector Kevin Brown earlier said.
Berezovsky, once known as 'the grey cardinal' of Kremlin politics, turned a fierce critic once he fled to Britain in 2000. He was granted political asylum by the UK in 2003 and several extradition requests by Moscow were turned down prior to his death.
The Russian oligarch's close associates hinted at the possibility of a suicide after he lost a $6bn (£3.95bn; €4.7bn) legal battle to his former business partner Roman Abramovich. He had earlier survived several assassination attempts.
Meanwhile, Moscow has said it would try to bring back the assets acquired by the former billionaire to Russia.
"As the Russian Criminal Code stipulates confiscation of property [as punishment] for setting up and participating in a criminal group, the Russian Prosecutor General's Office will continue its legal action aimed at bringing back to Russia the assets that Berezovsky and his accomplices illegally acquired and legalised abroad," said Deputy Prosecutor General Alexander Zvyagintsev, according to Ria Novosti.
Although Berezovsky's occupation and specific activities during the 1990s were never made clear, he amassed a fortune following the collapse of Soviet communism. He was later given a six-year jail sentence in absentia by a Russian court for stealing millions of dollars from the airline Aeroloft.
Another jail sentence for 13 years was also given to him in 2009 for stealing thousands of cars from Avtovaz during the same period.