Authorities in the United States are preparing to charge several traders and computer hackers over allegations of making illegal attempts to access press releases about unannounced mergers and acquisitions to trade on, the Wall Street Journal reported, citing people familiar with the matter.

On Tuesday, federal prosecutors in Brooklyn, New York, and the state of New Jersey are expected to charge over a half dozen people, who are accused of securities fraud and other charges related to an illicit scheme, which may have helped the group net tens of millions of dollars in illegal profits by trading on news not yet publicly available, the Journal reported.

According to the Journal's sources, the hackers allegedly compromised the computer systems of news-wire services that publish press releases about mergers and acquisitions. The intruders would then obtain information from confidential statements about unannounced deals, and use them to make early trades before those agreements were made public.

The charges expected on Tuesday are the result of a cross-agency investigation, involving at least six federal agencies. Top officials from those agencies include U.S. Secretary of Homeland Security Jeh Johnson and Mary Jo White, chairwoman of the Securities and Exchange Commission (SEC), the Journal reported.

As part of the investigation, the SEC asked at least eight listed companies in June to provide details of their data breaches. The insider trading probe was prompted by a December report by FireEye Inc., a Silicon Valley-based cybersecurity company, about a sophisticated hacking group, dubbed “FIN4.” According to the FireEye report, “FIN4” has tried to hack into email accounts at more than 100 companies since mid-2013, to access confidential information on mergers and other market-related events. 

“We suspect they are Americans, given their Wall Street inside knowledge,” Jen Weedon, FireEye’s manager of threat intelligence, told Bloomberg in December. “They seem to have worked on Wall Street.”

According to the FireEye report, more than 60 targeted companies were from the biotechnology and other healthcare-related fields. Weedon also said at the time that FireEye turned over the information it gathered to the FBI.

In 2005, the SEC charged an Estonian financial-services firm and two of its employees for trading in advance on more than 360 confidential press releases issued by over 200 U.S. public companies. The authorities alleged that the defendants stole information from a website of Business Wire, and made at least $7.8 million in illegal profits in a single instance. The firm later agreed to pay more than $14 million in penalties, the Journal reported.

“Access to insider information that could make or break stock prices for over 80 publicly traded companies could surely put FIN4 at a considerable trading advantage,” FireEye said in its report.