Updated on April 3 at 9:58 p.m. EST

News organizations from around the world have published investigations based on a massive trove of leaked documents they say reveal corruption and questionable business dealings of world leaders, politicians, sports stars, and others.

The German newspaper Süddeutsche Zeitung said Sunday it received encrypted internal documents from Mossack Fonseca, a Panama-based company that sells offshore shell companies around the world, from an anonymous source more than a year ago. The leak amounts to approximately 11.5 million documents—or 2.6 terabytes’ worth of data—on 214,000 shell companies spanning a period between the 1970s and 2016.

The documents, which have been dubbed the “Panama Papers,” contain mostly emails, PDF files, and photo files belonging to Mossack Fonseca, one of the largest providers of offshore financial services. They may represent the world’s biggest-ever leak of classified information.

“The data provides rare insights into a world that can only exist in the shadows,” Süddeutsche Zeitung said in its report. “It proves how a global industry led by major banks, legal firms, and asset management companies secretly manages the estates of the world’s rich and famous.”

Süddeutsche Zeitung shared the information with the International Consortium of Investigative Journalists and more than 100 news outlets in nearly 80 countries. Almost 400 journalists have combed through the documents over the past year.

Some of the products of that research were published Sunday. The BBC reported the leak reveals information about 12 current or former heads of state, including Syria’s president Bashar al-Assad, Egypt’s former president Hosni Mubarak, and Libya’s former leader Muammar Qaddafi. It reported Icelandic Prime Minister Sigmundur Gunnlaugsson stored millions of dollars of investments in Iceland’s major banks in an offshore company. The Guardian reported that Russian President Vladimir Putin’s associates secretly moved as much as $2 billion through offshore accounts. Sueddeutsche Zeitung reported Juan Pedro Damiani, the Uruguayan lawyer who is president of the country’s most popular soccer team and a FIFA ethics expert, managed companies through which FIFA members may have received bribes.

Owning an anonymous shell company is not illegal. It’s also pretty easy to set one up, as Fusion’s Natasha Del Toro showed Sunday, when she reported she had opened one in Delaware, a state known for its corporate-friendly privacy laws, for an anonymous owner—her cat. Shell companies allow their owners to hold assets that are subject to minimal governmental oversight. Some are used to dodge taxes—especially in tax havens, the name given to countries that offer foreign businesses little or no tax liability—and other criminal activity.

The reports published Sunday only scratch the surface of the leaked material, which eclipses in size the WikiLeaks dump of American diplomatic cables in 2010 and Edward Snowden’s disclosures in 2013. An untold number of stories emerged from those leaks and continue to pour out today. The first reports from the Panama Papers mark the beginning of a steady drip of potentially incriminating information.