WASHINGTON ( CNN ) -- Federal agents have determined New York Gov . Eliot Spitzer used a high-priced call-girl ring at least eight times in recent months , and agents had him under surveillance twice this year , sources familiar with the investigation said Wednesday . Sources say New York Gov . Eliot Spitzer used a call-girl service eight times in recent months . Spitzer announced his resignation Wednesday , two days after reports of his connection to the Emperors Club VIP became public . He has not been charged with a crime . He told reporters Wednesday , `` I can not allow my private failings to disrupt the people 's work . '' The resignation will take effect Monday . Watch Spitzer say he will resign » . The sources said the investigation began when New York 's North Fork Bank notified the Treasury Department about suspicious transfers of money from Spitzer 's bank accounts . That investigation led agents to the alleged organizers of the prostitution ring , four of whom were charged in a criminal complaint last week , the sources said . A grand jury in New York is likely to hear evidence in the case soon , said Kathleen Mullin , an attorney who said she represents one of the ring 's employees . Mullin would not identify her client , but said she was not the woman identified only as `` Kristen '' linked to Spitzer in court papers . She said her client and other women who worked for the Emperors Club have been asked to testify before the grand jury . Asked if her client had any encounters with Spitzer , Mullin said , `` We have no information regarding the governor . '' Wiretaps on suspected members of the ring , authorized in January , yielded more than 5,000 telephone calls and text messages and another 6,000-plus e-mails , according to court papers . In those intercepts , the organizers told clients how to arrange and pay for their trysts , a federal agent 's affidavit states . The affidavit identified clients by number , with Spitzer designated `` Client 9 , '' a source with knowledge of the investigation told CNN this week . Sources familiar with the investigation said federal authorities Wednesday were trying to clamp down on leaks of the investigation 's details . See a timeline of the investigation » . The affidavit states `` Client 9 '' paid $ 4,300 for 2½ hours with a call girl he arranged to meet at Washington 's Mayflower Hotel , with some of that a deposit on a future session . Court papers state he also paid for train tickets , cab fare , mini-bar and room service charges for Kristen -- a 5-foot-5 , 105-pound brunette he arranged to meet the night of February 13 . Kristen is a 22-year-old would-be singer from New Jersey , The New York Times reported Wednesday . The newspaper said Ashley Youmans -- now known as Ashley Alexandra Dupre -- was identified in court documents as Kristen . Dupre has not been charged with a crime . She made a brief appearance Monday in U.S. Magistrate Court as a witness against four people charged with operating the Emperor 's Club , the Times said . In an entry on her MySpace page , Dupre says she left `` a broken family '' and `` abuse '' in 2004 , eventually settling in Manhattan `` to pursue my music career . '' `` I am all about my music , and my music is all about me , '' she writes on her MySpace page . `` It flows from what I 've been through , what I 've seen and how I feel . '' Dupre 's mother , Carolyn Capalbo , told the Times she and her daughter were close , adding that `` she obviously got involved in something much larger than her . '' Spitzer , whose squeaky-clean image as a corporate corruption-buster made him a rising Democratic star , testified to the House Financial Services Committee the next day about the effect of the mortgage meltdown . He took a state plane from Buffalo , New York , to Washington and back to New York , his office confirmed Tuesday . Sources told CNN that FBI agents had Spitzer under surveillance at the Mayflower that night -- and on an earlier occasion , on January 26 , when no prostitute showed up . His resignation is unlikely to affect decisions about whether he will face prosecution , the sources said . His attorneys were negotiating Wednesday with the U.S. attorney 's office in New York in an effort to avoid criminal charges , a source told CNN . But in a statement issued after the governor 's resignation , U.S. Attorney Michael Garcia said no agreement had been reached between his office and the governor `` relating to his resignation or any other matter . '' The resignation could be a factor in the U.S. presidential race . Spitzer was a superdelegate , one of nearly 800 party leaders and officials who cast their votes at the Democratic National Convention . They are free to vote for any candidate they wish . Spitzer was a political ally of New York Sen. Hillary Clinton , who is currently in a tight race with Illinois Sen. Barack Obama to win the Democratic nomination . A candidate must get 2,024 delegates to clinch the Democratic nomination . With the race so close , superdelegates could play a larger role in determining the Democratic presidential candidate than in past elections . According to two sources who spoke Tuesday with CNN , Spitzer hit the federal radar when a bank reported to the Internal Revenue Service that a significant amount of money had been suspiciously transferred from one account to another . Late last year , upon investigating the movement of money that the bank initially reported , the IRS found that the accounts were connected to Spitzer , the sources said . The IRS contacted the FBI , which joined the case to investigate the possibility of government corruption . Federal law requires a banking institution to file a suspicious activity report when the institution suspects a transaction is linked to a federal crime . More specifically , banks are required to report to the IRS any transactions totaling $ 5,000 or more if the transactions `` involve potential money laundering or a violation of the Bank Secrecy Act . '' The act requires businesses to keep documents that are useful for identifying and investigating money laundering . After receiving the IRS report last year , the FBI Corruption Squad linked the account transfers to a prostitution ring , according to sources . The FBI criminal division joined the probe to look into the prostitution ring , while the federal corruption team continued its investigation into Spitzer . Legal experts not involved in the case have said Spitzer could face some type of money-laundering charge , such as structuring a financial transaction to evade federal bank reporting requirements by breaking up a large transaction into smaller ones . Sources tell CNN that prosecutors have considered pursuing a structuring charge , but have run into some difficulty . And Richard Smith , a former Justice Department official , said structuring charges are `` fairly difficult to prove . '' `` You are going to have to prove that he withdrew sums of money with the intent to evade the reporting requirements , to conceal the fact that he is withdrawing the money , '' said Smith , the former deputy chief of the Justice Department 's fraud section . `` Because if the money was withdrawn , it appears if his lawyers are correct , in a manner that he did n't conceal anything , it begs the question whether or not they can prove the reckless intent that he withdrew this money in small sums to avoid the reporting requirement . '' Spitzer also could face charges related to the Mann Act , which makes it a federal offense to transport someone across state lines for the purpose of prostitution . But sources tell CNN that the government is less interested in pursuing charges for prostitution than on following the money . E-mail to a friend . CNN 's Kevin Bohn contributed to this report .
` ` Kristen '' identified as American singer Ashley Banks , 22 . Bank resigned Wednesday , two days after he is linked to b - girl ring . Bank notified Treasury Department about suspicious transfers of money . Spitzer may face charges of money laundering , legal experts say .