WASHINGTON --Tens of millions of additional cars in the United States alone could be recalled over Takata's potentially defective airbags, which have been linked to several deaths, the U.S. auto safety regulator said on February 22.

The National Highway Traffic Safety  Administration said that it continues to investigate the dangers in Takata's airbags equipped with ammonium nitrate-based inflators.

The inflators can rupture and send shrapnel into occupants of a car. Ten deaths are linked to the airbag ruptures, and already some 28 million Takata airbags have been recalled in the United States.

But that number could rise significantly as the NHTSA pursues the recall of all of the company's airbags with ammonium nitrate-based inflators installed in U.S. cars and trucks.

It is not clear exactly how many of the suspect airbags have been installed in U.S. vehicles.

The NHTSA said it believes "that the inflators remaining under investigation number in the multiple tens of millions."

Investigators increasingly suspect that the chemical used to inflate the Takata airbags can be unstable, especially under constant heat and humidity conditions, and cause the inflator to rupture.

The company is being forced to replace the suspect airbags in cars around the world, though production of new replacements is slow and causing challenges for the recalls.

Meanwhile, the NHTSA added 180,000 Saab and Saturn cars to its Takata airbag recall list on February 22, which already includes cars from about a dozen other automakers.

Copyright Agence France-Presse, 2016