"In the process of the investigation, bank accounts have been blocked in Switzerland and an analysis has been created of money movement," the public
prosecutors office told AFP in an email sent late Wednesday in response to questions about the Russian money laundering enquiry.
The prosecutor's office said it could not provide further information or reveal the names of those who held the frozen bank accounts for now.
Last week, the Swiss daily Tages-Anzeiger reported that bank accounts containing millions of dollars had been frozen.
The case is linked to Magnitsky, a lawyer who worked for the Western investment fund Hermitage Capital, and who died in 2009 from untreated illnesses while awaiting trial for tax evasion.
Magnitsky was charged after claiming that Russian tax officials had fraudulently taken over three of Hermitage Capital's subsidiaries to recuperate a reported $230 million in tax refunds.
The money was believed to have been subsequently laundered through Swiss banks.
Hermitage Capital said in May 2011 that Swiss authorities had frozen the Credit Suisse accounts held by the husband of a former Russian tax official, Olga Stepanova, at the heart of the case.
The fund hailed on Thursday the news that Swiss prosecutors had broadened their probe.
"All financial transactions leave a permanent and inerasable trail," it stressed in a statement.
"Those who were connected to the theft and laundering of the money, and the false arrest and killing of Sergei Magnitsky to cover it up may be able to get away with murder, but they wont be able now to hide the proceeds of their crime in the West," it added.
The Magnitsky affair has sparked a heated row between Washington and Moscow, with the United States passing a law sanctioning Russian officials
implicated in Magnitsky's death.
Russia retaliated with a ban on the adoption of Russian children by families in the US that took effect on January 1st.