Only later, after more customers reported incidents of Dell laptops overheating or catching fire, did Dell realize that millions of its notebook PCs -- not just thousands -- could be at risk, according to records from government regulators and interviews with Dell spokesmen.

Letters from a top official at the U.S. Consumer Product Safety Commission to a Dell lawyer, obtained by CRN under the Freedom of Information Act, show that Dell reported to regulators on Oct. 24, 2005, that overheating problems with Sony battery packs were under review. Within weeks, Dell knew the exact defect causing the problems.

"Thank you for your full report of November 10, 2005. ... In your report, submitted on behalf of Dell Inc. ... you indicated that some lithium-ion battery cells manufactured for Dell could contain contaminates that create an internal short circuit," wrote Richard Stern, acting associate director of the CPSC, in a letter to John A. Hodges, a Washington, D.C.-based outside counsel for Dell.

"An internal short circuit could result in excessive heat, smoke or flames in the battery pack and possibly beyond, creating risk of thermal burn," Stern wrote.

On Dec. 16, 2005, Dell and the CPSC announced the 22,000-unit recall. Units affected, according to the announcement, were in Dell notebooks sold "from October 5, 2004, through October 13, 2005." (Documents obtained by CRN from the CPSC under the Freedom of Information Act can be downloaded here in PDF format.)

In its subsequent recall of 4.1 million units, announced Aug. 15, Dell said suspect units were actually sold between April 2004 and July 2006. Eight of the notebook models included in the December 2005 recall were also named in the later recall. As recently as last week, Dell expanded its recall to 4.2 million units.

What happened between recalls, if the same problem -- internal contamination -- was found in batteries made by the same manufacturer -- Sony -- in eight of the same notebook models? Dell said the more notebooks that caught fire, the more data it had to examine, and the better able it was to determine the precise volume of bad batteries it had shipped to the market.

Within months of the first recall notice last year, news and Internet reports began to surface of serious incidents of Dell laptops catching fire. The most notorious of those reports involved a laptop that exploded during a business conference in Japan, which was captured in photos. Those photos circulated over the Web and helped spark a major controversy for Dell.