The National Highway Traffic Safety Administration withheld from the public hundreds of pages of research and warnings about the hazards of drivers using cell phones.
The documents were released Tuesday by the Center for Auto Safety and Public Citizen, according to The New York Times.
The agency was afraid it would draw the wrath of Congress, if their findings were released.
Dr. Jeffrey Runge, the former head of the Traffic Safety Administration, told The New York Times on Monday that he was urged to withhold the findings, because some lawmakers warned the agency against lobbying states.
Runge said transit officials warned him against the billions of dollars that could be lost if the reports were made public.
The report found that driver distraction contributed to about 25 percent of all police-reported traffic crashes. The research also found that even with hands-free devices, a cell phone conversation took the driver's focus off of the road.
Some critics said the agency's decision to withhold the information from the public has resulted in traffic deaths and allowed the number of drivers who multitask while driving to increase.