Japan is investigating complaints of overheating iPod Nanos that got hot enough to scorch nearby paper and a woven straw mat. Apple claimed that the overheating was due to faulty batteries and acknowledged that "in very rare cases" first-generation iPod Nanos sold from September 2005 to December 2006 can overheat.

Apple admitted that it has received reports that less than 0.001% of first-generation iPod Nano units have had this problem, and have traced this problem to a single battery supplier.

Apple did not reveal the name of the supplier. Apple advised iPod Nano customers with an abnormally hot or overheating battery to contact AppleCare.  Those found to have faulty batteries will be replaced at no charge by Apple. The overheating of the iPod Nano causes "failure and deformation of the iPod Nano.”

The iPod Nano was released in September 2005, and its second generation version came out about one year afterward and third version of the Nano is expected to be announced shortly.