Federal safety regulators are investigating airbag inflaters made by ARC Automotive, a Tennessee supplier that uses the same explosive compound that has plagued inflaters made by Takata, public documents posted Tuesday showed.
The inquiry by the National Highway Traffic Safety Administration widens for the first time an investigation into explosive airbags beyond Takata, the manufacturer behind a defect blamed for eight deaths and more than 100 injuries worldwide.
The defective airbag inflaters can rupture when they are triggered in an accident, sending metal shards into the car. Takata has agreed to recall 34 million inflaters over the defect, affecting 11 automakers in the United States.
According to a document posted on the N.H.T.S.A. website Tuesday, the agency is investigating inflaters made by ARC Automotive, based in Knoxville, Tenn., that are used in about 420,000 2002 Chrysler Town and Country minivans, and about 70,000 2004 Kia Optima sedans.
The investigation was prompted by two reports of airbag ruptures, in a Town and Country minivan in 2009 and in a Kia Optima sedan in 2014.
The agency was alerted to the 2009 rupture in Ohio, which injured the driver, in December 2014, but concluded that it was an isolated event, the document said. But last month, Kia notified the agency of a lawsuit that said an inflater had ruptured in an Optima sedan in New Mexico, also injuring the driver.
Federal investigators then found that both incidents involved inflaters made by ARC that use ammonium nitrate to help generate the gases that inflate the airbag. The Kia airbag was assembled by the parts supplier, Delphi, and the Town and Country airbag was made by Key Safety Systems. “At the present time it is unknown if there is a common root cause in these incidents,” the safety agency said.
Takata has acknowledged that ammonium nitrate can break down over time, especially when exposed to high humidity, making the compound prone to combust violently.
The driver in Ohio, Lois Dutton, was struck by a snowmobile as she turned in to her driveway in January 2009, according to a lawsuit Ms. Dutton filed later that year against Key Safety Systems.
In an interview last year, Ms. Dutton said that she “saw a cloud of white smoke and a flash of white” as the airbag ruptured upon impact. Shrapnel sliced through an artery in her neck, and she passed out, she said.
“It looked like someone had shot a gun at the windshield,” she said.
Messages left with ARC on Tuesday evening were not immediately returned.
A Kia spokesman, Scott McKee, did not return requests for comment. Eric Mayne, a spokesman for Fiat Chrysler, said that the automaker was cooperating and that Chrysler no longer used the inflater model in question.