The attorneys general of New York and Connecticut are investigating Apple's negotiations with music companies to look for signs of potential antitrust violations.
The attorneys general want to know whether music labels colluded or were pressured into favoring Apple's paid music subscription service, which was released on Monday.
Apple launched Apple Music on Monday, a $9.99-a-month streaming music service that will likely alter the dynamics of how consumers listen to music as the music industry grapples with declines in downloaded songs and tries to figure out new ways to get people to pay for music.
In a letter to the New York Attorney General, Universal Music Group said it had no agreements with Apple or music companies like Sony Music and Warner Music that would impede the availability of free or ad-supported services, or prevent it from licensing its recorded music to any music streaming service.
Universal Music also said it offers limited exclusive content to some music streaming services where such exclusivity is not part of an agreement to restrain competition.
"This letter is part of an investigation of the music streaming business, an industry in which competition has recently led to new and different ways for consumers to listen to music," said Matt Mittenthal, a spokesman for the New York attorney-general, Eric Schneiderman.
"To preserve these benefits, it's important to ensure that the market continues to develop free from collusion and other anticompetitive practices."
An Apple spokesman declined to comment on the investigation. Connecticut Attorney General George Jepsen could not be reached for comment at the time of publication.