Federal authorities say the investigation began last October when the IRS received a report from a bank about suspicious activity connected to an account controlled by Spitzer.
Initially believing the activity could involve bribes, the Justice Department asked the FBI's public corruption squad to join the investigation.
It was only later, authorities say, that federal agents learned Spitzer had been moving the money to pay for the prostitutes. They say his movement of "tens of thousands of dollars" to pay for sex with call girls from the Emperor's Club may have violated federal money laundering laws.
Ironically, the financial crimes he may be charged with are some of the same crimes he prosecuted as New York's attorney general in his meteoric rise to prominence.