WASHINGTON - The National Highway Traffic Safety Administration said July 14 it hasn't yet reached any conclusions about whether driver error is responsible for the sudden-acceleration episodes that led to last year's Toyota recalls, the Associated Press reported.

The agency, which is part of the U.S. Transportation Department, said its engineers were continuing to investigate the possible causes of sudden and unintended acceleration in Toyota vehicles, along with scientists and researchers with the National Academy of Scientists and NASA.

The National Academy of Scientists is engaged in a broader probe of unintended acceleration. Its investigation is looking at vehicles across the entire auto industry, not just Toyota. The group's special panel is expected to report its findings in the fall of 2011.

The NHTSA statement came after a Wall Street Journal report earlier this week claimed that the government has analyzed dozens of event data recorders in Toyota vehicles involved in sudden-acceleration crashes, and that evidence suggests driver error was a recurring cause. The newspaper cited anonymous sources.

Toyota said its own investigation has found a number of explanations for the sudden acceleration, including floor-mat pedal entrapment, sticking gas pedals, and driver misapplication of the gas pedal. The automaker said it has found no evidence that electronic throttle control was a cause.