The government has reported another case of an iPod Nano overheating and urged people who use the portable music players to be cautious.

The iPod emitted sparks while it was being recharged last month in Tokyo, the 18th such incident in Japan involving the Apple Inc. product, the Ministry of Economy, Trade and Industry said.

The incident damaged part of the music player's control wheel but did not cause any injuries.

METI said the sparks were apparently caused by overheating of the product itself, and said officials were investigating further.

The iPod's model number is MA004J/A, the ministry said.