Japan says iPod nanos may pose overheating risk

The country's Ministry of Economy, Trade, and Industry said Tuesday that it had received two additional reports of iPod nanos that caught fire after overheating.

The incidents involve the following model numbers: MA004J/A, MA005J/A, MA099J/A, and MA107J/A, which encompass about 1.81 million units sold in Japan between September 2005 and September 2006. Neither of these most recent events caused injury, although earlier incidents were to blame for at least two cases of minor burns.

Another nano had produced sparks in March, and the Ministry had launched an initial investigation into its cause at that time. A total of 14 similar cases have been reported to Apple, the agency said.

Lithium-ion batteries are used within iPod, and are also commonly used in other consumer electronics devices. However, some manufacturers have been forced to recall them due to overheating issues, including Sony, which recalled millions of its laptop batteries.

Apple did not immediately respond to requests for comment, although Japanese broadcaster NHK reported that the company had no plans for a recall. It said Apple was ready to replace any defective parts, however.

Ministry officials have warned users with the nanos in question about handling during recharging. Apple itself has spoken somewhat on the subject: Some protective cases may cause the device to build up excess heat during the recharging process.