The National Highway Traffic Safety Administration said on Wednesday it has closed an engineering analysis into General Motors prior recall of more than 1.3 million of its vehicles in the United States for seat belt issues.

Following a four-year investigation involving approximately 1.3 million vehicles, NHTSA's Office of Defects Investigation is ending its probe into a slate of General Motors vehicles. The office looked at the failure of flexible steel seat belt anchor cables in the front seats of multiple vehicle models at risk of detaching and increasing the potential for injury.