The National Highway Traffic Safety Administration (NHTSA) has opened a preliminary investigation into Mercury Grand Marquis and Ford Crown Victoria cars for lighting issues.

The agency is probing around 520,000 2003-05 Ford Crown Victoria and Mercury Grand Marquis after it received a defect petition over the loss exterior lighting including headlights.

The NHTSA has reviewed 605 reports that have alleged failure of headlight. The complaints said both low-beam headlights failed particularly while driving, The Detroit News reported. Most of the complaints said the headlights failed suddenly and without warning.

“However some report the headlights flickered or dimmed prior to turning off. In some cases drivers were able to turn the headlights back on after a period of time while others reported the headlights would not come back on at all. Consumers noted they were able to hold the ‘flash to pass’ lever on the steering column mounted stalk to activate the high beams; however this is only effective as long as the lever is actuated,” NHTSA said.

“Within Ford’s complaints, there are 11 reports alleging a crash occurred. These drivers reported hitting objects, including other vehicles after the headlights failed causing damage to the affected vehicles. One driver was injured when their car struck an unseen object in the road, jerking the steering wheel from their hands and injuring their shoulder. In total 15 crash allegations were identified, all of which have occurred since 2008,” the agency added.