FILE PHOTO: The 2018 Volkswagen Tiguan is unveiled during the North American International Auto Show in Detroit, Michigan, U.S., January 8, 2017. REUTERS/Brendan McDermid

WASHINGTON (Reuters) - The U.S. National Highway Traffic Safety Administration said Friday it has opened a preliminary investigation into whether seat belts on new 2018 Volkswagen Tiguan sport utility vehicles could fail during a crash.

The agency said during crash testing in December the driver seat belt webbing completely separated, prompting the investigation into whether the issue could occur in consumer driving. A Volkswagen AG VOWG_p.DE spokeswoman said Friday the Tiguan has performed well in other tests and the automaker "will fully cooperate with NHTSA in the investigation and work to identify the cause of the different results between NHTSA's and our internal testing." VW introduced the new longer, three-row Tiguan in the United States last year as it expands offerings of larger vehicles for American buyers.