LONDON (AP) — British officials are investigating the unexplained death of a Russian businessman, a key witness against Russian officials who allegedly stole $230 million from a London hedge fund in a money laundering scheme.

Alexander Perepilichny's body was discovered Nov. 10 outside his rented house south of London. Police said a second post-mortem on the 44-year-old former milk factory owner would begin Friday after a previous one had proven inconclusive. It could still take months to get the new toxicology results, Surrey Police spokeswoman Nicola Burress said.

The case evokes memories of the 2006 death of former Russian spy-turned-Kremlin critic Alexander Litvinenko, who was poisoned with polonium-210, a rare radioactive isotope that was secretly slipped into his tea at a London hotel. The case took relations between Moscow and London to a post-Cold War low, a relationship that has yet to fully recover.

The latest Russian death is linked to the same money laundering scheme that was being investigated by Sergei Magnitsky, a Russian lawyer hired by the London-based hedge fund Hermitage Capital. Magnitsky died in a Moscow jail in 2009 amid torture claims, and his death has spurred efforts in Europe and the U.S. to punish Russian officials who may have been complicit in human rights abuses.

"All of us are at risk in this campaign," Hermitage Capital director William Browder told The Associated Press on Thursday.

Perepilichny had approached Hermitage officials in 2010 and provided extensive documents on the alleged scheme, Browder said. Bank statements, company registry documents and ownership records of offshore companies were then passed onto Swiss investigators and Hermitage Capital applied to file a criminal complaint in Switzerland.

Swiss Federal Prosecutors' Office spokeswoman Jeannette Balmer said Thursday that the Hermitage Capital investigation was ongoing but that some bank accounts had already been frozen.

Hermitage claimed the husband of a former Moscow tax official used bank accounts at Credit Suisse to make million-dollar property purchases after she approved a fraudulent $230 million tax return for three of Hermitage's subsidiaries. Their ownership documents had earlier been seized by officials at Russia's Interior Ministry, who used them to register their own people as owners and directors before filing the fraudulent tax claim, according to Browder, who has been waging a campaign against corruption in Russia for years.

Perepilichny, who owned a milk factory in the Ukraine and had been involved in investment management for others, never revealed to Hermitage how he had obtained the records, Browder said.

Perepilichny was cooperating as a whistleblower and had been aware of reports that his life had been threatened, according to a British official who spoke on condition of anonymity because he was not authorized to speak to the media.

"He came here a couple of years ago but his name had become known to us prior to his arrival in the UK," said the official. There had been reports that Perepilichny had become entangled with criminal gangs in Russia but he had not sought protection from authorities, the official said.

Perepilichny was living with his wife and two children in Weybridge, south of London.

Magnitsky was jailed by Russian officials after being charged with tax evasion linked to his defense of Hermitage. After officers at the Interior Ministry had seized ownership documents and registered their own people as owners and directors, they then reportedly filed a tax claim, saying they made a much smaller profit than originally described and asked for a $230 million tax return, according to Hermitage.

Magnitsky and Hermitage accused employees of the tax office that authorized the massive return in just one day of profiting from that tax scheme. The Interior Ministry has acknowledged the fraud but insisted that their tax officials played no part in it.

Russian criminal gangs are alleged to have helped in the money laundering scheme and Perepilichny is one of four men linked to the money laundering investigation who have died young.

Sergey Albayev, the alleged driver of a Russian gang leader, died in 2005 of heart failure at the age of 39. Alexei Alexanov, a 46-year-old linked to an alleged shell company, died in 2006 of heart failure. Valery Kurochkin, 43, who also had links to criminal gangs, died of liver disease in 2008.

Earlier this month, the U.S. House of Representatives approved a measure that imposes visa and financial restrictions on Russian officials linked to human rights abuses. Browder, who has pressed for such restrictions, plans to push for similar measures in Canada next week.

Many Russians who have fled to the U.K. for various reasons have reported being targeted.

In March, a former Russian banker was shot in an apparent assassination attempt in east London after giving evidence in a 2009 attempted murder case. German Gorbuntsov suffered several gunshot wounds outside an apartment block close to London's Canary Wharf financial district. Scotland Yard is still investigating the shooting.