(Reuters) -- Mazda Motor Corp. will broaden a recall of cars sold in the United States because an airbag inflator, supplied by Japanese supplier Takata Corp., could rupture and seriously injure occupants.
The issue of ruptured inflators -- which can hurl metal shrapnel at vehicle occupants -- has bedeviled Takata and triggered the recall of millions of vehicles. The company supplied the parts to at least nine global automakers.
The recalls were expanded this year as issues cropped up in newer models equipped with Takata airbags and inflators.
In a filing Friday with the National Highway Traffic Safety Administration, Mazda said it would recall about 18,000 older models, including 18,000 Mazda6 sedans and 50 RX-8 sports cars from 2003-04.
NHTSA said the inflator could rupture, "with metal fragments striking and potentially seriously injuring" occupants.
Mazda dealers will replace for free the passenger-side airbag inflator, beginning in August.
Separately, NHTSA said it had opened investigations into cars made by Hyundai Motor Co. and Chrysler Group.
NHTSA said it was investigating nearly 400,000 2006-08 Hyundai Sonata sedans after receiving complaints that the seat belt buckle assembly had failed. The safety agency said the problem could cause airbags to fail in a crash.
It was also investigating about 123,000 2011-12 Dodge Chargers over complaints about engines stalling and alternator failure.
Mazda's expanded U.S. recall is part of a global recall of nearly 160,000 vehicles for similar issues announced by the company on June 23.
Over the past five years, about 12 million vehicles equipped with Takata airbags have been recalled around the world for similar issues.
Last week, German automaker BMW said it would recall another 1.6 million cars with Takata airbags because of the risk of injury from inflators that could rupture.