(Reuters) - BMW AG (BMWG.DE) will get five more months to acquire Takata 7312.T air bag replacement parts for a massive recall because tests showed some of the substitute inflators may also be defective, the U.S. auto safety agency said on Thursday.
The deadline for the German automaker was extended to Aug. 31 because a replacement driver-side air bag inflator made by a supplier other than Takata failed during testing, the National Highway Traffic Safety Administration (NHTSA) said.
"NHTSA's priority continues to be ensuring that unsafe air bag inflators are replaced with safe ones," the agency said in a statement.
A BMW spokeswoman declined to comment.
Takata inflators can explode with excessive force and spray metal shrapnel into vehicle passenger compartments, and have been linked to 10 deaths worldwide and more than 100 U.S. injuries. To date, 14 automakers have recalled about 24 million vehicles involving about 28 million Takata air bag inflators.
NHTSA said all automakers besides BMW have reported that they are on track to meet the original March 31 deadline under a agency order to supply enough replacement inflators for "priority one" vehicles, with the highest risk of ruptures. The agency set the deadline in early November.
The consent order also set deadlines of Sept. 30 for automakers to have enough replacement parts for "priority two" vehicles, and Dec. 31 for "priority three" vehicles. NHTSA will delay those deadlines for BMW until 2017.
The delays affect 420,000 recalled vehicles, including several types of BMW 3-series, 5-series and the X5, NHTSA said. About 100,000 of these are priority one cars.
BMW told NHTSA in January that it had obtained replacement inflators from a supplier which it did not identify, and then reported subsequent testing failures to the agency.
The automaker requested a five-month extension in February.
The extension applies only to one type of inflator and not to other Takata inflators in vehicles manufactured by BMW.
BMW said it was working on three alternative designs as a backup plan if the current redesigned part fails.
BMW told NHTSA in a Feb. 23 letter released by the agency on Thursday that it believed the root cause of the test failures "relates to unanticipated interaction with the horn plate in the steering wheels."
Until then, BMW will continue its "like-for-like remedy program until an alternate inflator is available," NHTSA said.
In late December, NHTSA named John Buretta, a former official in the Justice Department's criminal division, to serve as independent monitor overseeing the Takata recalls.
Reporting by David Shepardson; Editing by Richard Chang