Vladimir Markin said that Khoroshavin's real estate and other property is valued at well over the aggregated income of his family over the past years.
"One of the versions about where such wealth came from is graft from companies that was set up like a 'conveyor,'" the spokesman said.
Markin noted that Khoroshavin received a $5.6 million bribe from Sakhalin Enterprise Energostroy company.
Khoroshavin was arrested earlier in March on accusations of accepting a bribe for awarding a contract for the construction of a thermoelectric plant in Sakhalin.
Russia's Investigative Committee stated that around 1 billion rubles (around $16 million) in different currencies, as well as large amounts of jewelry and a pen worth 36 million rubles, were found during searches of Khoroshavin's apartment.