WASHINGTON -- The 2010 Kia Soul, a boxy vehicle that has been marketed to urban motorists, is being investigated by government regulators for potential loss of steering control.

The National Highway Traffic Safety Administration said Monday on its website that it had received one complaint alleging steering loss. The preliminary investigation covers more than 50,000 vehicles.

The complaint claims that the steering shaft detached from the steering wheel, leading to a complete loss of steering, and that the shaft fell into a position that interfered with the driver's ability to brake.

The government agency seldom opens an investigation based on one complaint but said it was "very concerned about this failure in that it occurred without warning on a new vehicle at low mileage and resulted in a complete loss of steering as well as a compromised brake system."

The owner who filed the complaint had driven the vehicle for two months and had 4,300 miles on it.

John Crowe, Kia Motors America's vice president for service, said in a statement that the company was cooperating and trying to determine if there was a manufacturing cause to the problem. He said the incident that led to the complaint did not result in an accident or injury.

The Soul was among 27 vehicles from the 2010 model year that received the "top safety pick" award from the Virginia-based Insurance Institute for Highway Safety. Vehicles are selected for providing the best protection in front, side and rear crash tests based on Institute evaluations during the year.