By David Shepardson
WASHINGTON (Reuters) - The U.S. National Highway Traffic Safety Administration said on Thursday it is upgrading a probe of more than 8 million air bag inflators made by ARC Automotive Inc after a driver was killed in Canada when an inflator ruptured in a Hyundai vehicle last month.
The investigation covers inflators used by General Motors Co <GM.N>, Fiat Chrysler Automobiles NV <FCHA.MI>, Hyundai Motor Co <005380.KS> and Kia Motors Inc <000270.KS> and covers at least 8 million inflators used by the automakers through 2004, but could include newer vehicles, the agency said. Canadian regulators are also investigating.
ARC did not immediately respond to a request for comment.
NHTSA spokesman Bryan Thomas said the agency will "direct the collection and testing of inflators as part of its effort to determine the root cause of the rupture incidents."
The upgrade comes as regulators are intensely scrutinizing air bag inflators following a series of fatalities in vehicles with Takata Corp <7312.T> inflators.
Upward of 100 million vehicles worldwide with Takata airbag inflators have been declared defective and are linked to 13 deaths and more than 100 injuries. Takata inflators can explode with too much force and spray metal shrapnel into vehicle passenger compartments.
NHTSA said the ARC inflators are a hybrid design using high- pressure stored gas and a small amount of ammonium nitrate to inflate the air bags. It said its preliminary investigation shows "significant design differences between the ARC inflators and the Takata inflators currently under recall."
NHTSA initially opened an investigation on 490,000 vehicles 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.
The upgrade comes after confirmation that a July 8 fatal crash in Newfoundland and Labrador was tied to an ARC air bag inflator rupture. The fatality was in a 2009 Hyundai Elantra with an inflator assembled in China.
The 2009 Elantra sold in the United States did not use the Chinese-made inflator, NHTSA said in a filing, adding that it is not clear if any of those Chinese-made ARC inflators were sold in U.S. vehicles.
GM, Fiat Chrysler and Hyundai all said they are fully cooperating with NHTSA's investigation.
(Reporting by David Shepardson; Editing by Dan Grebler)