WASHINGTON, July 31 (Reuters) - The National Highway

Traffic Safety Administration said Wednesday it still believes

51 million air bag inflators in 49 million U.S. vehicles

assembled by 13 automakers pose serious safety risks despite

objections from the auto sector.

The issue has been linked to one U.S fatality and seven

injuries following an eight-year government investigation. If

the recall proceeds, it would be the second-largest in U.S.

history.

NHTSA argued at a hearing in October that inflators produced

by the two air bag manufacturers, ARC Automotive and Delphi

Automotive, should be recalled because they may rupture and send

metal fragments flying. After automakers raised objections in

December, the agency did not immediately finalize its decision.

The agency said Wednesday it was reiterating and updating

its initial determination first issued in September and giving

automakers another 30 days to respond before it could formally

demand recalls.

"Common sense demands acknowledging that metal shrapnel

projecting at high speeds and causing injury or death presents

an unreasonable risk to safety," NHTSA said.

Major automakers including General Motors ( GM ), Toyota

Motor ( TM ) and Volkswagen and the two air bag

makers in December said they opposed NHTSA's bid to seek

recalls.

Automakers and a major trade group did not immediately

comment Wednesday.

Reuters reported in October that at

least 20 million GM vehicles

could be affected, while Stellantis ( STLA ) has 4.9 million

vehicles with inflators at issue and has reported just one

rupture, in 2009.

Automakers and manufacturers said the risks from the issue

were exceedingly small, questioning the agency's analysis and

rationale for seeking a recall.

The inflators in question had been used in vehicles

produced from 2000 through early 2018 by 13 automakers including

Jaguar Land Rover. Ford, Mercedes-Benz, BMW

, Hyundai, Kia and Porsche also

oppose a mandatory recall.

NHTSA first called for a voluntary recall in May 2023,

but ARC rejected it.

GM, which in May 2023

recalled 1 million

ARC inflators after a rupture resulted in facial injuries

to a driver, said in December a recall would affect "as much as

15% of the over 300 million registered motor vehicles in the

United States."

Delphi Automotive, part of Autoliv ( ALV ), manufactured

approximately 11 million of the inflators through 2004 under a

licensing agreement with ARC, which manufactured the remaining

40 million.