The vehicles include: 2007 Toyota Camry and RAV4; 2007-2009 Toyota Yaris; and the 2008 Highlander Hybrid.
Many of the complaints filed with NHTSA state that the driver was simply cruising along when he or she smelled smoke. Within a few minutes, the flames would appear near the window switch.
"After exiting the vehicle, the flames quickly increased and began shooting into the air uncontrollably," one person said in their complaint about their 2007 Camry. "This incident, fortunately, did not lead to any serious physical injuries, however, the emotional trauma and distress caused by the ordeal is long lasting."
Toyota, which is well known for using common parts across its vehicle lineup, could see the number of vehicles continue to grow even higher during the investigation.
While Toyota has not issued a recall for these switches, expanding the investigation is not good news for the automaker still struggling from the millions of vehicles it had to recall last year for a series of problems. Another million-vehicle-plus recall would further dampen enthusiasm for the Japanese company, which has long been considered the standard bearer for quality and reliability.
Additionally, NHTSA the same day it announced its expanded probe into Toyotas that it was also continuing its investigation in the Chevrolet Trailblazer for door fires. The investigation impacts 342,000 SUVs.