Apple is now warning users of iPod Nano 1st generation users, for it may become overheats, and cause safety risks.
Nanos produced (or sold) during September 2005 to December 2006 may rarely have defective batteries. The problem only happens “rare cases,” still Apple recommends user to stop using 1st generation iPod nano.
Apple posted following instructions and information on its website, including how to order a replacement unit. -R