The problems for Japanese auto parts maker Takata Corp (7312.T) grew after U.S. safety regulators expanded a warning about faulty air bags to 6.1 million vehicles in the United States while two more lawsuits have been filed over accidents in older Honda cars.

The news came a day after Toyota Motor Corp (7203.T) recalled 247,000 vehicles in the United States because of potentially defective Takata air bags that can rupture and spray metal shrapnel at occupants.

"The National Highway Traffic Safety Administration (NHTSA) urges owners of certain Toyota, Honda, Mazda, BMW, Nissan, Mitsubishi, Subaru, Chrysler, Ford and General Motors vehicles to act immediately on recall notices to replace defective Takata air bags," the regulator said in a statement on Tuesday.

"Over six million vehicles are involved in these recalls, which have occurred as far back as 18 months ago and as recently as Monday."

The previous NHTSA warning, issued on Monday, covered 4.74 million vehicles, and dragged Takata's shares down 23 percent on Tuesday in Tokyo, the stock's biggest-ever one-day drop.

Its shares were initially up 7.5 percent early on Wednesday, but quickly fell back to trade flat, leaving them down 44 percent so far this year.

In a statement released before the most recent NHTSA warning was issued, Takata said it would cooperate with U.S. authorities and automakers.

Takata said the cost of repairs for the 4.74 million vehicles subject to the NHTSA's earlier bulletin had been set aside, and that any additional costs would be minimal.

The U.S. House Energy and Commerce Committee said on Tuesday it was seeking information about the air bag defects from NHTSA and automobile manufacturers.

Democratic Senator Bill Nelson of Florida, where some of the air bag incidents have occurred, wrote to NHTSA Deputy Administrator David Friedman urging the agency to further expand the recalls.

"NHTSA should ensure that owners of cars that are not registered in Florida, but spend a substantial portion of the year operating in the state of Florida are covered by the recall," Nelson wrote.

He was referring to "snowbirds", people who spend winters in Florida to escape the cold in the northern part of the United States.

Cars produced by nine automakers including Toyota, Honda Motor Co Ltd (7267.T) and Fiat Chrysler Automobiles' (FCHA.MI) Chrysler Group are affected by regional recalls that started in June.

They began in certain high-humidity areas of the United States after the NHTSA started investigating reports of air bag explosions in Florida and Puerto Rico.

GLOBAL RECALL

The NHTSA is investigating whether Takata air bag inflators made between 2000 and 2007 were improperly sealed. Bags inflating with too much force have been linked to four deaths and resulted in several lawsuits.

More than 16 million vehicles globally have been recalled because of defective Takata air bags since 2008.

The two accidents resulting in lawsuits against Honda and Takata both took place in Florida.

A Honda spokesman declined to comment on both lawsuits because they are pending. A Takata spokesman referred questions to Honda.

According to an accident report and lawsuit filed in July in a Florida state court, Corey Burdick, 26, was driving his 2001 Honda Civic in Eustis, Florida, on May 29 when he was involved in an accident with another vehicle.

The accident report said an eye injury Burdick suffered was "possibly caused by the air bag deployment." The lawsuit, which is seeking damages above $15,000, said "shards of metal were propelled through the air bag's fabric and struck Corey Burdick in the eye, resulting in disfigurement, impaired vision and other severe permanent injuries."

In the second accident, Stephanie Erdman, a then 28-year Texan stationed at a military base in Florida, was driving her 2002 Civic in Santa Rosa County when she was involved in an accident with another vehicle on Sept. 1, 2013, according to an accident report and lawsuit.

The lawsuit described how "shards of metal, like shrapnel, were propelled toward Stephanie Erdman ... striking (her) in the face and right eye." It included a picture of her bloody face and the metal lodged in her eye.

Erdman's lawsuit, which is seeking more than $1 million in damages, was filed in May in Texas, where she bought the car.

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