(Reuters) – The National Highway Traffic Safety Administration (NHTSA) demanded the recall of 67 million air bag inflators because it believes there is a safety defect, but auto supplier ARC Automotive Inc rejected the U.S. regulator’s request, documents released on Friday show.

The auto safety agency said the inflators pose an unreasonable risk of death or injury.

Even as ruptures mount, “ARC has not made a defect determination that would require a recall of this population,” NHTSA said in its demand letter to the Tennessee-based company. “Air bag inflators that project metal fragments into vehicle occupants, rather than properly inflating the attached air bag, create an unreasonable risk of death and injury.”

ARC air bag inflators are in General Motors (GM.N), Chrysler-parent Stellantis (STLAM.MI), BMW (BMWG.DE), Hyundai Motor (005380.KS), Kia Corp (000270.KS) and other vehicles. GM on Friday agreed to recall nearly 1 million vehicles with ARC air bag inflators after a rupture in March resulted in facial injuries to a driver.

ARC rejected NHTSA’s tentative conclusion that a defect exists saying it is based upon seven field ruptures in the United States. NHTSA “then asks ARC to prove a negative – that the 67 million inflators in this population are not defective” that were produced over 18 years. The company said it will continue to work with NHTSA and automakers to evaluate ruptures.

NHTSA in 2016 upgraded a probe of more than 8 million air bag inflators made by ARC after a driver was killed in Canada in a Hyundai vehicle and has been investigating more than seven years.

NHTSA initially opened an investigation in July 2015 following two reported injuries.

NHTSA said through January 2018, 67 million of the subject driver and passenger frontal air bag inflators. Delphi, acquired by Autoliv (ALV.N), manufactured approximately

11 million of the inflators under a licensing agreement with ARC, which manufactured the remainder of the inflators.

ARC noted there have been several testing programs of inflators collected from scrapped or other vehicles but not a single rupture occurred during these tests.

The 67 million inflators were produced for the U.S. market on multiple production lines across different plants and used by 12 vehicle manufacturers in dozens of models. “None of these manufacturers has concluded that a systemic defect exists across this broad population,” ARC said.

NHTSA said that ARC in January 2018 completed installation of devices on inflator manufacturing lines used to detect excessive weld slag or other debris. NHTSA said it is unaware of issues in ARC inflators produced since then. ARC said weld slag has not been confirmed as the root cause in the ruptures.

NHTSA has been scrutinizing air bag inflator ruptures for more than 15 years.

Over the last decade, more than 67 million Takata air bag inflators have been recalled in the United States and more than 100 million worldwide, the biggest auto safety callback in history.

More than 30 deaths worldwide — including 24 U.S. deaths — and hundreds of injuries in various automakers’ vehicles since 2009 are linked to Takata air bag inflators that can explode, unleashing metal shrapnel inside cars and trucks. The latest death was in July 2022 in a 2010 Chrysler 300, one of three Stellantis deaths in a seven-month period.