Japan is investigating a potential defect in an early generation iPod nano after one of the players reportedly emitted sparks while recharging.

Japan's trade and economy ministry said local authorities are investigating to find out if a defect affects the lithium-ion batteries installed within the device.

The event took place in January in Tokyo. Apple reported the problem to the ministry, no one was injured in the incident.

Apple Japan must now find out what caused the fire and report back to the government. Associated Press reveals the affected iPod nano had the following model number: model number MA099J/A.

Apple has shipped about 425,000 units of the affected model in Japan. The model was discontinued in September 2006.