Toyota had "not been able to single out or verify any other cause" for the unintended acceleration, the company said when the floor-mat recall was made.

At first the National Highway Traffic Safety Administration (NHTSA) and Toyota thought that a badly fitting floor mat could have jammed the accelerator open.

Alongside the floor mat trouble, Toyota last week recalled 2.3 million us cars and trucks because of problems with sticking accelerator pedals.