April 20 (Bloomberg) -- Sony Corp., which recalled a record 9.6 million laptop batteries last year, said a study on the cause of the battery malfunctions will reiterate earlier findings that blamed metal particles and chargers.

In October, the company said metal particles that got into battery cells during the manufacturing process caused short circuits, leading to overheating. Battery charging units also played a role in the malfunctions, the company said then.

``There are no changes'' in the determination of the causes, said Chisato Kitsukawa, a Tokyo-based Sony spokesman, confirming an earlier report by the Nikkei newspaper.

The company will submit the findings to the U.S. Consumer Product Safety Commission this month, the Nikkei said. Kitsukawa declined to specify to what organization and when Sony plans to file the report.

The recall, the biggest in the consumer electronics history, drained 51.2 billion yen ($431 million) from Sony's earnings as the world's second-largest consumer-electronics maker shouldered the cost of replacing power cells in laptops made by customers including Dell Inc., Apple Inc. and Lenovo Group Ltd.

Japan Electronics and Information Technology Industries Association and the Battery Association of Japan will release new safety guidelines today that effectively ban rapid battery recharges for laptop computers because of the risk of overheating, the Nikkei said. The guidelines are not legally binding, it said.

Sony's shares rose 0.8 percent to 6,460 yen on the Tokyo Stock Exchange as of 1:23 p.m. The stock has gained 36 percent in the past six months.

To contact the reporters on this story: Yoshinori Eki in Tokyo at yeki@bloomberg.net; Pavel Alpeyev in Tokyo at palpeyev@bloomberg.net.

Last Updated: April 20, 2007 00:26 EDT