The U.S. International Trade Commission said it is investigating Apple based on a complaint filed by Nokia in late December, indicating that the dispute between the companies is heating up.
In its complaint, Nokia charged Apple with infringing seven of its patents in virtually all of Apple's phones, music players and computers. Nokia asked the ITC to order Apple to stop importing and selling the offending products.
Apple, in mid-January, similarly asked the ITC to investigate Nokia, charging the phone maker with infringing its patents. The ITC has not yet responded to Apple.
The companies have also taken their complaints to the courts. Nokia has filed a patent infringement suit against Apple in the U.S. District Court for the District of Delaware. Apple countersued, charging Nokia with infringing 13 Apple patents.
The ITC will set a timeline for completing its investigation within 45 days. Once the investigation is complete, six of the ITC's administrative law judges will make an initial determination about the case. That initial determination is then subject to review by the full commission.