U.S. law enforcement is taking a keen interest in the so-called Panama Papers. The document trove, a 40-year cache of communications and files from Panama City-based international law firm Mossack Fonseca, details how various heads of state, their friends and families, athletes, FIFA execs and other celebrities and billionaires hide their assets behind shell companies located in tax havens like the British Virgin Islands.

The 11.5 million documents were originally leaked to German newspaper Süddeutsche Zeitung in late 2014 and were provided to more than 100 news outlets through the International Consortium of Investigative Journalists, which started publishing the accounts Sunday night. The documents named several past and present officials of FIFA, the world soccer governing body that is the target of a corruption probe by the U.S. Justice Department.

A spokesman for the DOJ said the agency is reviewing the reports and looking for all connections to the U.S. financial system. "While we cannot comment on the specifics of these alleged documents, the U.S. Department of Justice takes very seriously all credible allegations of high-level, foreign corruption that might have a link to the United States or the U.S. financial system," spokesman Peter Carr wrote in an email.

It's not just the DOJ. The Department of Treasury is looking at the trove of documents as well, with an eye toward who might be illegally evading U.S. taxes, through its Office of Foreign Assets Control. "The U.S. government intently focuses on investigating possible illicit and sanctions evasion activity using all sources of information, both public and non-public," a Treasury spokeswoman said in response to a query about the Panama Papers.

The document leak includes 2.6 terabytes of information, and spans business conducted with more than 14,000 clients since the law firm's founding in 1977. Among the names are 12 current or former heads of state and 61 associates of national leaders, including associates of Russian President Vladimir Putin, who is alleged to have $2 billion in shell corporations set up through Mossack Fonseca. 

Named in the documents are major global banks such as Credit Suisse, HSBC and USB, as well as 500 other financial institutions. Many of the financial institutions connected to these deals are based, or have offices in, the U.S., meaning they're within the jurisdiction of U.S. law enforcement. The law firm at the center of the leaks, Mossack Fonseca, said in a statement that it has "operated beyond reproach" for 40 years and has never faced criminal charges.

So far, strikingly no U.S. citizens have been named as part of the leaks, leading some to presume that many more revelations are yet to come. In addition, leading American newspapers such as the New York Times, Wall Street Journal, Washington Post and others were omitted from list of 109 global media companies receiving the data, in favor of regional newspapers like the Miami Herald and Charlotte Observer, and new media outlets like Fusion.