A new federal investigation of the Ford Crown Victoria centers on the vehicle's rear axle design.
The Detroit News reports the National Highway Traffic Safety Administration launched the probe last week, after receiving complaints from two police departments.
The police reported four separate incidents in which Crown Victoria axles had fractured or the rear wheel assembly had separated.
The Crown Victoria has been battered by complaints from police departments nationwide. At least 14 officers have died in fire-related crashes since 1983.
The agency says it wants to gather more information about the alleged safety problem. The latest probe covers the Mercury Grand Marquis and Lincoln Town Car sedans as well as the Crown Victoria.