Government intensifies probe into Ford floormats The nation's top auto-safety regulator has escalated and broadened an investigation into sticking floormats in Ford, Lincoln and Mercury vehicles that could cause sudden unintended acceleration. This week the National Highway Traffic Safety Administration upgraded the probe, originally launched in May 2010, to an engineering analysis, its highest and most serious grade of investigation. In addition, it expanded the scope to include almost twice as many vehicles as originally being reviewed. Under review are 2008 through 2010 Ford Fusion, Mercury Milan and Lincoln MKZ sedans; previously only the 2010 Fusion and Milan were being considered. All told, an estimated 480,000 vehicles could be affected. According to the safety agency, it has received 52 consumer complaints about the problem, many of which describe sedans accelerating out of control and being extremely difficult to stop as the engine roars. No accidents, injuries or fatalities have been reported, and the agency said that drivers were able to stop their vehicles by shifting into neutral or turning off the ignition. NHTSA said that the acceleration may be caused by sticking floormats. "The accelerator pedal may fail to return to idle due to interference created by unsecured or double-stacked floor mats in the driver's foot-well," the agency report, dated Dec. 12, said. Susan Krusel, spokeswoman for Ford, said the automaker was "disappointed with this upgrade, particularly since this investigation relates to unsecured, improperly installed or double-stacked floormats. But we will continue to cooperate fully with the agency throughout this process. In 2009, the NHTSA opened a similar investigation into sudden acceleration in a variety of Toyota vehicles, concluding that floormats could cause dangerous sudden acceleration. That led to a series of recalls of Toyota and Lexus vehicles for a variety of problems that could cause vehicle speed control and braking problems. In all, the Japanese automaker recalled more than 10 million cars and trucks worldwide and paid record fines to NHTSA of nearly $50 million. In June, Toyota recalled an additional 150,000 Lexus RX crossovers for floormats that can depress the gas pedal. Toyota Camry is top-selling car but faces stiff competition Honda recalls more than 800,000 vehicles for ignition issue GM aims to reverse market share slide with all-new Chevy and GMC pickups