Suspicious trading in Dow Jones shares before the US media firm received a $5bn (£2.5bn) takeover bid earlier this month is being investigated.
Investigators want to know who knew what and when
The New York Attorney General and the Securities and Exchange Commission are looking into trading patterns in share options ahead of News Corp's shock bid.
Trade in call options - which allow investors to buy shares at a later date for a set price - soared in late April.
Dow Jones owns the Wall Street Journal and other business titles.
Dow Jones revealed on 1 May that it had received a surprise bid from the Rupert Murdoch-controlled company.
The bid resulted in a 50% rise in the firm's shares.
Market regulators and state authorities are concerned about the amount of trading in share options in the days before news of the takeover bid emerged.
This was far higher than for the first three months of the year combined, arousing suspicion that some people may have been aware of an imminent bid.
Call options can be hugely lucrative if share movements can be accurately predicted.
Dow Jones and News Corp have both received subpoenas for information from the New York Attorney General's office and inquiries from the Securities and Exchange Commission.
The two companies said they would co-operate "fully" with the investigations.
The Bancroft family, which controls the majority of Dow Jones shares, has said it is opposed to the bid, although some members are thought not to share this view.