The National Highway Traffic Safety Administration said the problem was limited to 2000-2003 model Taurus and Sable cars, as they were the only models with a throttle assembly that was the cause of the problem.
The Detroit News reported Saturday regulators had received 50 complaints of throttles becoming jammed after a plastic bracket that holds the throttle cable in place had broken.
Ford is "aware of NHTSA's preliminary investigation ... and will cooperate fully with the agency as we conduct our analysis," said company spokeswoman Marcey Zweibel.
Ford had "just begun" its own investigation, she said.
"And we have very limited information at this time," she added.
The problematic speed control mechanism only appears in cars with 4-valve 3.0L V6 Duratec engines, the News said.
The NHTSA concluded an investigation this week into jammed throttles involving 2005-2006 Taurus and Sable models.
The regulator said drivers were able to stop those vehicles if they encountered problems.