New York State Attorney General Letitia James announced Tuesday that 47 attorneys general from states and U.S. territories plan to take part in a New York-led antitrust probe into Facebook. Shares of Facebook fell 3.9% on the news.

The multistate investigation was announced in September with participation from seven other states, but it has since expanded to nearly the entire country. The probe will zero in on whether Facebook broke any state or federal laws as a result of any anti-competitive conduct related to its dominance of social media.

"After continued bipartisan conversations with attorneys general from around the country, today I am announcing that we have vastly expanded the list of states, districts, and territories investigating Facebook for potential antitrust violations," James said in a statement. "Our investigation now has the support of 47 attorneys general from around the nation, who are all concerned that Facebook may have put consumer data at risk, reduced the quality of consumers' choices, and increased the price of advertising. As we continue our investigation, we will use every investigative tool at our disposal to determine whether Facebook's actions stifled competition and put users at risk."