U.S. law enforcement agencies are investigating reports that Russian hackers infiltrated the Dow Jones business news service and stole information to trade on before it was made public.
Bloomberg reported that the breach was "far more serious than a lower-grade intrusion" disclosed by the company last week, and it has been under investigation for a year by the Federal Bureau of Investigation, Secret Service, and Securities and Exchange Commission.
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.
Dow Jones also said there was unauthorized access to its systems at certain times between August 2012 and July 2015.
The hackers sought information, including stories being prepared for publication, which could yield profitable trades in financial markets, Bloomberg said.
"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," a Dow Jones spokeswoman said.