By David Shepardson

WASHINGTON (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. "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," NHTSA said in its demand letter.

ARC air bag inflators are in General Motors, Chrysler-parent Stellantis, BMW, Hyundai Motor and Kia Corp 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.

NHTSA in 2016 upgraded a probe of more than 8 million air bag inflators made by ARC Automotive Inc 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, in a 2002 Chrysler Town & Country and a 2004 Kia Optima, after inflators produced by ARC in Tennessee ruptured.

NHTSA said through January 2018, 67 million of the

subject driver and passenger frontal air bag inflators. Delphi, acquired by Autoliv, manufactured approximately

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

ARC said NHTSA's tentative conclusion that a defect exists 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.

(Reporting by David Shepardson; Editing by Leslie Adler and David Gregorio)