British authorities say a Russian businessman linked to a high-profile Russian corruption scandal has died under mysterious circumstances.

Local police tell VOA that they are treating the death of Alexander Perepilichnaya as unexplained. They are awaiting results of toxicology tests and a second autopsy.

The 44-year-old Perepilichnaya collapsed and died outside his mansion south of London on November 10. Police did not make the case public until Wednesday after a first post-mortem examination proved inconclusive.

Perepilichnaya had sought refuge in Britain three years ago after giving evidence to Swiss authorities on a Russian mafia money-laundering scheme.

He also had provided evidence against suspects linked to the 2009 death of Sergei Magnitsky. The Russian anti-corruption lawyer died in jail after exposing a massive tax fraud scheme.

Several other people tied to the Magnitsky case have died under mysterious circumstances, and British media reports say Perepilichnaya had apparently been in good health prior to his sudden death.

The Magnitsky case prompted the U.S. House of Representatives to approve a bill this month that would upgrade U.S. trade relations with Russia while punishing Russian officials for human rights violations.

The House bill would ban visas for, and freeze the bank accounts of, about 60 Russians believed to have taken part in Magnitsky's arrest and who are allegedly responsible for his death. The measure now goes to the Senate for further approval.

The Russian government has strongly protested the bill.