Federal investigators executed a search warrant at Microsoft's Mountain View, Calif., offices earlier this month as part of an investigation into a high-priced call girl ring similar to the one used by former New York Gov. Eliot Spitzer.

Court records show that that an Internal Revenue Service agent carried out the search order at Building 4 of Microsoft's Mountain View campus on March 4.

The investigator, IRS special agent Anthony Romero, was seeking the Microsoft Hotmail account records of a woman accused of involvement in a pricey escort service operating out of Denver, Colo. Records show that Romero seized from Microsoft more than 3,000 files of "preserved data" from the account of [email protected].

Authorities believe that "Kitty Crimson" is actually Heather Bruck, a Denver-area woman who allegedly worked as a prostitute for an escort service that went by the names Denver Sugar and Denver Players, according to court papers.

The ring, which charged clients upwards of $400 an hour for sex, catered to prominent and wealthy Denver residents, including businessmen and professional athletes, according to local media reports.

Denver's Rocky Mountain News last week reported that the chief judge of the U.S. District Court for Colorado, Edward Nottingham, has also been identified as one of the escort service's customers.

Nottingham presided over the insider trading trial of Joseph Nacchio and last year sentenced the former Qwest Communications CEO to six years in federal prison. Nacchio recently had his conviction overturned and a new trial was ordered.

Denver Sugar/Denver Players was allegedly operated by a woman named Brenda Lynn Stewart, according to court documents.

Investigators allege that Stewart established a bogus tech services firm called Phoenix Media & Consulting LLC as a front through which she could funnel payments to and from her escorts and their clients.

In an odd twist, the woman accused of running the prostitution ring that ensnared Spitzer also used a tech services company as a front for her other business. Cecil Suwal allegedly laundered payments from the Emperors Club VIP escort agency through a company called QAT Consulting, which specializes in "online advertising and promotion services," according to its Web site.

No arrests have been made to date in connection with the Denver Sugar/Denver Players escort ring. There's no indication that Microsoft or any of its employees are involved with the ring.