U.S. authorities are reported to be investigating whether Russian hackers have infiltrated the Dow Jones financial news company to steal market-moving information prior to publication.
The breach was "far more serious than a lower-grade intrusion" a year ago, Bloomberg News reports, citing sources.
There has been no reaction from the White House or the State Department. But Bloomberg reports the Federal Bureau of Investigation, Secret Service and the Securities and Exchange Commission are leading the investigation, which began at least a year ago.
However, a Dow Jones spokeswoman expressed skepticism about the Bloomberg report. "Since Bloomberg published its article, we have worked hard to establish whether the allegations it contains are correct. To date, we have been unable to find evidence of any such investigation," Dow Jones spokeswoman Colleen Schwartz said in an email.
But the FBI confirms it is looking into the hacking incident, though it did not comment on whether other U.S. government agencies are doing so as well.
Dow Jones, the publisher of the Wall Street Journal and a unit of Rupert Murdoch's News Corp, disclosed last week a breach of its systems that put payment card and contact information of about 3,500 individuals at risk.
Bloomberg said the current hack is considered far more serious. The news agency said it was not clear if the two incidents were related.
Dow Jones had said that there was unauthorized access to its systems at certain times between August 2012 and July 2015.
Bloomberg said it was not clear if the information stolen included news stories, or embargoed financial data that had not yet been published.
"To the best of our knowledge, we have received no information from the authorities about any such alleged matter, and we are looking into whether there is any truth whatsoever to this report by a competitor news organization," said Dow Jones as quoted by the French News Agency (AFP).
The case comes on the heels of numerous other hacking episodes involving sensitive market information. U.S. prosecutors in August brought charges against a pair of hackers in Ukraine who stole unpublished corporate press releases from online public relations services like Business Wire and sold them to people who traded shares on the information.