The National Highway Traffic Safety Administration (NHTSA) has opened an investigation into around 500,000 older model Ford sedans for issues with the steering, reported Autoguide.com.

Following five complaints, the agency is probing 2004 through 2007 Ford Crown Victoria, Mercury Grand Marquis and Marauder models. The heat shield can dislodge and obstruct the steering shaft, leading to locking or stiffening of the steering.

One of the complaints, made to the NHTSA, included an injury.

Ford has called back many of these vehicles and intends to make another recall if a systemic problem is found in the investigation.