Russian opposition activist Alexei Navalny, founder of Anti-Corruption Foundation, wrote on Twitter on Monday that detectives were currently searching his brother's apartment.
Interfax has been unable to obtain confirmation of Navalny's words.
In December, brothers Alexei and Oleg Navalny were charged with fraud and money laundering.
"Alexei Navalny set up a limited liability company called Chief Subscription Agency and an acquaintance of his who had nothing to do with its subsequent business became its nominal founder and general director," Russian Investigative Committee spokesman Vladimir Markin told Interfax.
In spring 2008, Oleg Navalny, who at that time held a senior role at Russian Post, "tricked executives at one of the trading companies with foreign capital that was doing business on the territory of the Russian Federation to sign an agreement with Chief Subscription Agency on mail transportation," Markin said.
He said that between August 2008 and May 2011 Chief Subscription Agency carried mail for the foreign company between Yaroslavl and Moscow.
The transportation services cost a maximum of 31 million rubles, but the Navalny firm was paid more than 55 million rubles, Markin claimed.
The brothers used the bulk of this sum for their own needs, he said.
"To legalize the criminal money, the Navalnys transferred more than 19 million rubles out of that sum from the settlement account of the fake firm to the settlement account of the Kobyakovo Willow-Weaving Factory, whose founders included the brothers, for fictitious reasons and under fictitious agreements, for allegedly renting non-residential space and for materials," Markin said.
Operatives subsequently searched the Kobyakovo Willow-Weaving Factory and Oleg Navalny's office, and on Dec. 17 Alexei Navalny was notified that he was under prosecution on suspicion of embezzling 55 million rubles.
Alexei Navalny said the embezzlement proceedings were launched against him on Dec. 13. He said the reason was that that day he warned he would attend a demonstration on Lubyanskaya Square in Moscow on Dec. 15.
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