Washington -- The National Highway Traffic Safety Administration has opened a preliminary investigation into steering issues reported on the 2011 Hyundai Sonata.

NHTSA said it reviewed field reports on 2011 Hyundai Sonata vehicles that allege either a separation of the intermediate steering shaft assembly upper universal joint that resulted in a complete loss of steering capability or a loosening, but not complete separation, of the upper universal joint connection.

The probe covers about 16,300 2011 Hyundai Sonata vehicles, NHTSA said in a statement posted today on its website. The popular vehicle accounts for nearly half of the company's car sales in the United States.

The auto safety agency has taken a broad interest in steering issues in recent months, opening investigations after very small numbers of complaints or reports.

Earlier this month, NHTSA opened an investigation into possible loss of steering in the 2010 Kia Soul, after getting one complaint alleging total steering loss. That vehicle was 2 months old with 4,300 miles. NHTSA's investigation of the Kia Soul covers about 51,000 vehicles. The agency said it was "very concerned" because it occurred without warning and compromised the brake system.

Both South Korean automakers are controlled by a parent company, Hyundai Kia Automotive Group. The vehicles that reported problems were manufactured by Hyundai during the same month and had fewer than 600 miles of service at the time of the reports.

Hyundai spokesman Jim Trainor said the company isn't aware of any accidents or injuries connected to the issue and is fully cooperating with NHTSA in its investigation.

He said Hyundai had reports of two vehicles with a steering problem connected to the upper universal joint and both were repaired.

"No defect has been identified. It's too early to draw any conclusions about anything," Trainor said.