Two iPod nano owners in Japan have had a “fiery” experience with their gadgets, Japan officials reported today. The first incident took place in January this year, but it wasn’t until March that Apple reported the problem, while the second one took place earlier this month.

Both incidents have been investigated by Japan’s Economy, Trade and Industry Ministry. As it appears, none of the iPod owners suffered any injuries. Apple was not available for comments on the two incidents.

According to officials investigating the situation, it appears that the iPod nanos’ batteries may have been the main cause of the devices overheating. A possible defect on the lithium-ion battery is still being under investigation, since it appears that the iPods overheated while being charged.

Apple introduced the iPod nano on the Japanese market in September 2005, and has managed to sell over 400,000 units every year, facing an increasing demand.

After an iPod caught fire earlier this year, the Japanese authorities began an investigation in order to establish whether other iPod nano owners might be exposed to the same risk.

The lithium-ion rechargeable batteries are greatly used in consumer electronics, and most of all, they are used in portable electronics. Japan authorities are continuing their investigation in cooperation with Apple.

It still remains uncertain how these incidents will affect Apple in Japan, but it wouldn’t be for the first time that Apple had to recall some of its products due to overheating battery reports.

It seems like producers should pay more attention to the batteries they introduce on the market, as lithium-ion batteries in some laptops have also been blamed for a series of blazes, which forced Dell to make the biggest recall of laptops in its history in 2006.

In 2007, another “hot” incident occurred at Hartsfield-Jackson Atlanta International Airport, when an iPod nano caught fire…while peacefully sitting in somebody’s pocket.