Sometimes identity thieves are petty criminals, taking advantage of an opportunity that presents itself in the form of a lost wallet or carelessly junk mail. But often, identity theft is just part of wider criminal activity.

Stolen mail, credit card templates, methamphetamine and slot machines: that’s what investigators found a couple weeks ago when they busted a home nicknamed “the Castle” in San Francisco.

It’s not uncommon for criminals involved in identity theft to diversify their operations, using the proceeds from one arena of criminal activity to finance another. At the Castle, that meant taking stolen mail from drug addicts, and paying them off in methamphetamine. Money made from gambling at the small time, after hours casino no doubt contributed to the funds needed for the crime ring leaders to buy more meth.

Members of the Santa Clara County Rapid Enforcement Allied Computer Team found mail from at least 15 victims at the Castle. Apparently mailboxes belonging to the affluent residents of areas like Santa Clara and San Mateo counties were the favorite targets.

Personal and financial information—names, addresses and credit card account numbers—found in the stolen mail was then coded onto magnetic strips and embossed onto blank plastic credit cards. The fraudulent credit cards could then be used to purchase merchandise, which could then be sold to make more money.

The Castle and its residents were under investigation for roughly a year after police got information from informants about the illegal activity conducted there. Twenty-seven people were in the home when police made the arrests.