NEW YORK (CNNMoney.com) -- It's still early, but a government investigation into Toyota acceleration problems has found that drivers may have been at fault in many cases because they didn't properly apply their brakes.
Researchers for the government's National Highway Traffic Safety Administration looked into 58 crashes of Toyota cars from earlier this year.
In 35 of the cases, data recorders showed the brakes were never used. In 14 other cases, the brakes were only partially applied and, in one instance, both the gas and brake pedals were applied together. In five of the cases, the event data recorder was not triggered by an impact, so no data was recorded.
Toyota isn't fully in the clear, however. Toyota issued recalls earlier this year tied to two known problems: sticking gas pedals and pedals that could become stuck in non-standard floor mats. One of the 58 cases investigated involved "pedal entrapment."
And NHTSA still needs to conduct more tests to determine if there could have been other factors. For now, the agency stressed that the results are preliminary.
"At this early point in its investigation, NHTSA officials have drawn no conclusions about additional causes of unintended acceleration in Toyotas beyond the two defects already known," the agency said in its report to members of Congress.
NHTSA is also working with the National Academy of Sciences and the National Aeronautics and Space Administration on laboratory-based investigations into potential electronic or mechanical malfunctions in Toyota throttles. A report based on that investigation is expected in the fall.
Responding to the report, Toyota said it has also conducted many of its own investigations and has also found no additional problems.
Besides the two issues for which recalls were performed, other reasons for what drivers reported as "unintended acceleration" were situations in which the vehicle's engine speed normally rises - such as after a cold start or when the air conditioner turns on - or drivers mistakenly pressing the gas instead of the brake pedal, Toyota said.
Toyota also said, specifically, that it has not found electronic controls to be factor in any of the cases it has investigated. Some auto safety experts have associated Toyota's switch from mechanical to electronic throttle controls with an increase in unintended acceleration complaints.