U.S. officials revealed to NBC News that they have taken part in two global meetings about the Panama Papers to plan how to use the huge trove of leaked documents to catch criminals — and urged Americans to come clean now before illegal activity is discovered.

Last week’s discussions in Paris and Washington between IRS and Treasury officials and their counterparts from around the world are the first evidence of U.S. involvement in the growing international coalition eager to analyze and use the data about more than 214,000 offshore companies listed by Panamanian law firm Mossack Fonseca.

In a statement to NBC News, the IRS acknowledged participating in a “special project meeting” of JITSIC, the Joint International Tax Shelter Information and Collaboration network, about the papers in Paris last week.

The IRS also encouraged any U.S. citizens and companies that may have money in offshore accounts to contact the agency now before any possible illegal activity on their part is identified. According to media reports, the documents contain information on potentially thousands of U.S. citizens and firms that have at least an indirect connection to offshore accounts affiliated with Mossack Fonseca. Many other firms provide similar services, and the Treasury Department estimated last year that more than $300 billion dollars of illicit proceeds are generated in the United States annually, with criminals using such companies here and abroad to launder funds.

“People hiding assets offshore should recognize the continued changes and progress in the international tax arena,” the IRS said. “More than ever, their best option remains to come forward voluntarily and participate in the IRS Offshore Voluntary Disclosure Program.”

The 11.5 million confidential documents, leaked to German newspaper Süddeutsche Zeitung and shared with the International Consortium of Investigative Journalists, provide detailed information about how criminals, corrupt heads of state, celebrities and others have for decades been using secret hideaways in tax havens to launder money, evade taxes and hide other suspected criminal behavior.

Earlier, U.S. federal agents and prosecutors told NBC News that they had begun to mobilize in an effort to obtain and use the Panama Papers to bolster existing criminal investigations and prosecutions and to launch new ones.

The JITSIC meeting took place Wednesday at the Organisation (cq) for Economic Co-Operation and Development, and brought together senior tax officials from more than 40 countries. They discussed “opportunities for obtaining data, co-operation and information-sharing in light of the ‘Panama Papers’ revelations,” the OECD said in a statement.

IRS officials said they could not discuss who participated and what, specifically, was discussed. But in its statement to NBC News, the IRS described the meeting as “productive and timely” and said “governments around the world are working together cooperatively” to respond to the information released in the Panama Papers, with JITSIC playing a coordinating role.

“We will be closely monitoring the situation along with our international tax administration partners as we determine what steps to take to ensure compliance with U.S. tax laws and meet our shared global interests,” the IRS added.

This combination of pictures shows six world leaders (top from L) Argentinian President Mauricio Macri, Emirati President Sheikh Khalifa bin Zayed al-Nahayan and Saudi King Salman bin Abdulaziz, (bottom from L) Ukraine President Petro Poroshenko Prime Minister of Iceland Sigmundur David Gunnlaugss and British Prime minister David Cameron whose names are featured in a massive leak of documents from Panama-based law firm Mossack Fonseca. The storm unleashed by the so-called Panama Papers continued to swirl on April 7, 2016 as British Prime Minister David Cameron admitted benefiting from his father's offshore trust and prosecutors opened an investigation into Argentine President Mauricio Macri. / AFP PHOTO / --/AFP/Getty Images - / AFP - Getty Images

On Thursday, senior Treasury officials discussed the leaked documents – and the need for more information sharing and a crackdown on tax evasion – in gatherings that were part of the annual “spring meeting” in Washington of the International Monetary Fund and World Bank, according to a senior Treasury official.

After those meetings, bankers and finance ministers from the world’s 20 largest economies sent a warning to tax havens saying they would ramp up efforts to punish governments that continue to hide billions of dollars in offshore accounts.

“We need to act to deal with tax shelters and the problem of international tax system permitting havens to develop,” U.S. Treasury Secretary Jacob Lew said Friday.

Mossack Fonseca has denied any wrongdoing, saying it worked within existing laws and guidelines to help its clients set up legal accounts and that it was not aware of those accounts being used for illegal or illicit activities.