Toyota Motor Corp. first learned in 2008 about a defect in power-window switches that Wednesday prompted it to recall 7.43 million vehicles worldwide for fire hazards, according to documents filed with U.S. regulators.

Toyota received a report in September 2008 from the U.S. about "an unusual smell" from the power-window master switch and "thermal damage" to the switch, the company said in a report posted Thursday on the U.S. National Highway Traffic Safety Administration website.

The automaker sent the part to the supplier to investigate and no "root cause" was found. No other problems with the switch were reported until May 2010, when the company said it began sporadically receiving information about an abnormal smell or smoke coming from driver's side doors, according to the report.