Toyota's president said it was "extremely regrettable" an American family died in a crash in which a floor mat in one of the automaker's vehicles is suspected as the cause.

"Four precious lives have been lost," Toyota Motor Corp. President Akio Toyoda said Friday. "I offer my deepest condolences."

Without giving specifics, he said an investigation is under way into the problem, which may cause the accelerator to get stuck and could potentially affect 3.8 million Toyota vehicles in the United States.