U.S. auto safety regulators opened an investigation into Rivian Automotive Inc. over issues with the seat belts in its electric delivery vans that could introduce additional risk in the event of a crash.

The National Highway Traffic Safety Administration said it’s aware of six reports of potential failures with the seat belt anchorage system for the driver’s seat in Rivian’s vans. In multiple instances, the steel braided cable connecting the belt to the seat frame has frayed or broken, “leaving the occupants unrestrained in the event of a collision,” the agency said in a document posted to its website.

NHTSA’s Office of Defects Investigation opened a so-called preliminary evaluation to assess the severity and scope of the potential problem. The probe covers an estimated 17,198 Rivian vans produced between 2022 and 2023.

Rivian didn’t immediately respond to a request for comment.

The automaker produces delivery vans in large numbers for e-commerce giant Amazon.com Inc. Rivian, which is partnering with Germany’s Volkswagen AG, also makes plug-in pickups and SUVs for the consumer market.