Ford is recalling 1 million Mustang and GT sports cars because their driver's side air bags could potentially explode.

The air bags made by Takata Corp. can inflate with too much force, spewing shrapnel into the passenger compartment.

Ford recalled nearly 500,000 Mustangs and GTs for the problem in December. But facing government pressure, Takata agreed last week to expand the number of air bag inflators that need to be recalled to 33.8 million in the U.S.

As a result, Ford expanded its recall to include additional model years. Mustangs from the 2005 to 2014 model years are now included in the recall, as well as GTs from the 2005 and 2006 model years.

Takata to replace chemical in air bags

Ford will begin notifying owners next month. The company will replace the air bags for free.

A top Takata Corp. executive said the company plans to replace the chemical in its air bags that has been linked to a defect responsible for at least six deaths and more than 100 injuries.

Kevin Kennedy, executive vice-president of North America for Takata Corp., will also tell Congress the company "deeply" regrets every rupture episode involving its air bags, especially those causing injury or death. Kennedy says in written testimony for a U.S. House hearing Tuesday that the percentage of air bag inflators likely to have a problem is "extremely small" but Takata is replacing all of them.

The company has declared 33.8 million air bags defective in an agreement with U.S. regulators. It's the biggest auto-safety recall in U.S. history. 

takata airbag Hiroshi Shimizu

Takata executive Hiroshi Shimizu says more than 34 million vehicles with Takata airbag inflators have now been recalled in the U.S. Takata's executive vice-president of North America, Kevin Kennedy, has written a testimony for a U.S. congressional hearing on Tuesday. (J. Scott Applewhite/Associated Press)

The Takata air bag problems began surfacing about a decade ago. The ammonium nitrate can explode with too much force, blowing apart a metal inflator and sending shrapnel into the passenger compartment.

Takata's rivals use different kinds of inflator propellants other than ammonium nitrate.

"We are working with our automaker partners to transition to newer versions of driver inflators in our replacement kits, or inflators made by other suppliers that do not contain ammonium nitrate propellant," Kennedy said in testimony prepared for a House Energy and Commerce Committee subcommittee.

Although the National Highway Traffic Safety Administration and the auto industry are still trying to determine exactly what is causing Takata's inflators to explode, the agency said last week it decided the recall action needed to be taken immediately to protect the public.

Kennedy said there have been fewer than nine failures causing air bag ruptures in the U.S. out of every 100,000 air bag deployments. Most of them occurred in parts of the country with high heat and humidity, he said.

34 million cars recalled in U.S.

"It is unacceptable to us and incompatible with our safety mission for even one of our products to fail to perform as intended and to put people at risk," Kelly said in his written testimony.

Takata's agreement with NHTSA adds more than 18 million air bags to existing recalls, covering both the passenger and driver's side.

The agency sparred with Takata for the past year over the size of the recalls and the cause of the problem. For the most part, the air bag maker refused to declare the inflators defective and even questioned NHTSA's authority to order it to conduct a recall.