A number of fires involving overheating iPods in Japan, have been caused by overheating batteries, according to Apple.
In response to reports that Japan is investigating incidents of iPod nanos getting hot enough to scorch paper placed nearby, Apple acknowledged that "in very rare cases" first-generation iPod nanos sold between September 2005 and December 2006 can overheat.
This problem, which Apple said is extremely rare, causes "failure and deformation of the iPod nano".
The company said it has received reports about less than 0.001 percent of first-generation iPod nano units acting in this way, and has traced the problem to a single battery supplier. Apple did not name the supplier.
Apple added that there have been no reports of serious injuries or property damage due to the overheating problem, and no reports of incidents for any other iPod nano model.
The company advised iPod nano customers who have experienced an overheating battery or who have concerns to contact AppleCare. IPod nanos with faulty batteries will be replaced for free by Apple.
Apple's statement was in response to reports out of Japan Monday that the Japanese Ministry of Economy, Trade and Industry was investigating two separate incidents in Tokyo in which iPod nanos overheated, burning nearby paper and a woven straw mat.
In March, the Japanese ministry reported a similar incident, in which sparks flew out of an iPod nano.
Apple first released the nano version of its popular music and video player on Sept. 7, 2005. The second generation of the product came out about a year later.