WASHINGTON - U.S. auto safety regulators said on Tuesday that 52 million air bag inflators produced by auto suppliers ARC Automotive and Delphi Automotive need to be recalled because they may rupture and send dangerous metal fragments flying.

The National Highway Traffic Safety Administration (NHTSA) first demanded a voluntary recall in May, but ARC rejected it. The agency issued an initial decision on Tuesday and set a public meeting for Oct. 5 in a rare move to compel a recall.

If successful in forcing a recall, the callback would be one of the largest on record.

The inflators that NHTSA is seeking to have recalled have been used in vehicles from 2000 through early 2018 produced by 12 automakers, including General Motors, Ford Motor , Stellantis, Tesla, Toyota Motor , Hyundai, Kia, Mercedes-Benz , BMW and Volkswagen.

"Air bag inflators that rupture when commanded to deploy are plainly defective, as they both fail to protect vehicle occupants as they should, and, themselves, pose an unreasonable risk of serious injury or death," NHTSA said on Tuesday.

ARC in May rejected NHTSA's tentative conclusion that a defect existed. ARC did not immediately respond to a request for comment on Tuesday.

NHTSA said that ARC in January 2018 completed installation of devices on inflator manufacturing lines used to detect excesses of a hardened byproduct of welding known weld slag, or other debris.

The agency said it is unaware of issues in ARC inflators produced since installation of the devices. ARC said previously weld slag had not been confirmed as the root cause in the ruptures.

NHTSA said it "believes that the evidence does identify a likely cause" and added that ARC's argument on not finding a root cause "is not a reason for delaying a recall."

The agency said it is aware of seven confirmed inflator ruptures in the United States in the vehicles it seeks to have recalled, including seven injuries and one death.

Initially, NHTSA said 67 million air bag inflators were unsafe, but on Tuesday it adjusted that estimate to account for "over-inclusive responses reported to the agency by certain manufacturers over the course of the investigation."

GM in May agreed to recall nearly 1 million vehicles with ARC air bag inflators after a rupture in March resulted in facial injuries to a driver.

Delphi Automotive, acquired by Autoliv, manufactured approximately 11 million of the inflators through 2004 under a licensing agreement with ARC, which manufactured the remaining 41 million inflators. Autoliv did not immediately respond to a request for comment.

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 on record.

More than 30 deaths worldwide - including 26 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 May involving a Takata passenger-side bag.

(Reporting by David Shepardson; editing by Jonathan Oatis, Leslie Adler and Timothy Gardner)