US road safety bosses now believe that 89 people have died in sudden acceleration crashes involving Toyotas, rather than the 52 previously reported.
America's National Highway Traffic Safety Administration (NHTSA) says the deaths occurred in 71 accidents reported since 2000. Earlier, it had put the total at 43.
There has also been an increase in the number of reported complaints of sudden acceleration involving Toyotas. The NHTSA has now received 6200 complaints compared with 2600 when it previously reported in March.
However, the US regulators have found no evidence to warrant a new defect investigation after speaking to 100 of the complainants, said NHTSA administrator David Strickland.
Toyota has examined 2000 vehicles, and found no electronic flaws that would explain the reports of unintended acceleration, according to James Lentz, the company's sales president in the US.
The manufacturer is one of 11 car makers that have agreed in principle to fit brake-override systems to its cars from next year. This will give the brakes priority if the car's electronics send out simultaneous signals to brake and accelerate.
Toyota has also agreed to retro-fit seven current models with new software that will act as a brake-override system.