NEW YORK (CNN/Money) - The use of electronic devices such as cell phones, including hands-free, precipitated many crashes and near misses, according to a report Thursday.

Using a cell phone behind the wheel is a key cause of traffic accidents and hands-free devices provide little safety benefit, the Detroit News reported, citing federal officials.

National Highway Traffic Safety Administration researchers said devices like head sets or voice-activated dialing led to longer dialing times than for hand-held phones. The delays offset the potential benefit of keeping both hands on the wheel, the report said.

The research adds to a growing body of studies that suggest hands-free cell-phone systems do not deliver the safety benefits automakers and legislators had thought.

But whether drivers use a handheld device or not, "phone use degraded both driving performance and vehicle control," said NHTSA's Elizabeth Mazzae, according to the paper.

Hands-free devices can give drivers a false sense of security, as research has shown that it is the act of conversation that leads to distraction and inattentive driver behavior, NHTSA officials have said.

Auto companies have been conducting their own research to gauge how well hands-free devices help drivers stay focused, the report said.

Jeff Greenberg, director of Ford Motor Co.'s (Research) driving simulator, conducted several studies trying to break down which parts of cell- phone conversations impair drivers. It is too soon to know what to do, he said.

"The preponderance of evidence suggests that long conversations while driving impair your ability to react to events," Greenberg said, according to the paper. "But it would be difficult to make rules about conversations in vehicles."

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