The U.S. Federal Trade Commission (FTC) is looking into claims about whether Apple's treatment of rival streaming music apps is illegal under antitrust law. Apple recently launched a new music streaming service, Apple Music. It also provides the App Store platform for competing streaming services including Jango, Spotify, Rhapsody and others.

Apple takes a 30 percent cut of all in-app purchases for digital goods sold on its platform.

While $9.99 has emerged as the going monthly rate for music subscriptions, including Apple's, some streaming companies complain that Apple's cut forces them to either charge more in the App Store than they do on other platforms or erode their profit margins.

The Federal Trade Commission is looking at the issue but has not begun a formal investigation, according to Reuters. The agency has had meetings with multiple concerned parties, one source said. The agency meets with companies routinely, and a formal investigation may not materialize.

The FTC declined to comment.