Computer makers are recalling 100,000 laptop battery packs made by Sony Corp. after 40 reports of overheating, according to a U.S. Consumer Product Safety Commission notice Thursday.

The voluntary recall applies to certain Sony 2.15Ah lithium-ion cell batteries made in Japan and sold around the world in laptops made by Hewlett-Packard Co., Dell Inc. and Toshiba Corp.

Some incidents involved smoke or flames, according to Sony. Twenty-one of the reports claimed minor property damage, and small burns were reported in four cases.

Sony blamed two factors for the defects: adjustments on its manufacturing line from October 2004 to June 2005, which may have affected the quality of cells in certain production lots; and a possible flaw in the metal foil for electrodes.

The company said no reports have been filed for batteries made after 2006, and noted that the recalled units are a small fraction of the more than 260 million it has shipped over six years. This also pales in comparison to the recall of nearly 10 million of a different model of Sony batteries in 2006 and 2007, which affected almost every major PC manufacturer, including Dell Inc. and Apple Inc.

In this batch of problematic laptops, the bulk of the 35,000 affected computers in the U.S. were sold by HP between December 2004 and June 2006, according to the safety commission, including HP Pavilion, HP Compaq and Compaq Presario models.

Some Dell Latitude and Inspiron models shipped between November 2004 and November 2005 are also covered by the recall, as well as some Toshiba Satellite and Tecra laptops sold from April 2005 to October 2005.

An additional 65,000 of the flawed batteries were sold outside the U.S. The PCs and separate batteries were sold directly by the computer manufacturers, electronics stores and online retailers worldwide, not by Sony.

Sony said its own Vaio laptops don't use the battery in question. Last month, however, the company recalled 440,000 Vaio notebooks worldwide because of a wiring flaw that can cause overheating.

The safety commission said PC users should remove laptop batteries immediately and contact the manufacturer to request a replacement. Details, including laptop model numbers and contact information for Dell, HP and Toshiba, have been posted on the commission's website.

Shares of Sony rose $1.52, or 7.2 per cent, to close at $22.65 Thursday amid broader market gains.