The US International Trade Commission said it has begun investigating Apple over claims that its iPad and iPhone gizmos infringe patents belonging to a Taiwanese firm.
Elan Microelectronics complained at the end of March that the new iPad uses technology covered by its patents on multi-finger touch-screen input.
The Taiwanese company had already sued Apple, but reckoned the ITC complaint was a quicker way to enforce its patents.
The news comes just a few weeks after the ITC launched a separate patent probe, instigated by Apple, of HTC, another Taiwanese device maker.
It will take some months before the agency makes a decision. If Apple is found at fault, it could find sales of its devices legally halted.
Alternatively, the company could always just claim that it found the technology lying around in a pub.