Toyota Motor Corp (7203.T) recalled 247,000 cars, SUVs and pickup trucks in the United States on Monday because they are equipped with potentially defective front passenger air bag inflators from Japan's Takata Corp (7312.T) that can rupture and spray metal shrapnel, according to U.S. safety regulators.

That raised the number of vehicles affected by regional recalls launched in June by several automakers due to the Takata air bags to more than 4.5 million.

The regional recalls by Toyota and other automakers including Honda Motor (7267.T) and Fiat Chrysler Automobiles' (FCHA.MI) Chrysler Group began in certain high-humidity areas of the United States after the National Highway Traffic Safety Administration (NHTSA) started investigating reports of air bag explosions in Florida and Puerto Rico.

Prompted by NHTSA, Takata and automakers have been trying to determine whether exposure to high humidity caused any defect in the inflators collected though the regional recalls.

"At this point, the issue appears to be a problem related to extended exposure to consistently high humidity," NHTSA said in a statement on Monday. "However, we are leaving no stone unturned in our aggressive pursuit to track down the full geographic scope of this issue."

Toyota recovered replaced air bag inflators from areas of South Florida and Takata evaluated them starting in August, according to the NHTSA documents. On Oct. 10, Takata informed Toyota that a number of the inflators performed "improperly" during testing. Five days later, after reviewing the data with NHTSA, Toyota decided on the recall.

Over the last six years, Takata has recalled about 16 million vehicles globally for defective air bags, including the regional recalls.

The Toyota vehicles affected by Monday's recall are from model years 2002 through 2005, according to the NHTSA documents. They include the Lexus SC coupe, Toyota Corolla small car, Corolla Matrix small car, Sequoia SUV and Tundra full-size pickup. Also part of the recall are General Motors' (GM.N) Pontiac Vibe, which was built by Toyota.

The vehicles being recalled are registered or originally sold in areas of South Florida, along the Gulf Coast, Puerto Rico, Hawaii, the U.S. Virgin Islands, Guam, Saipan and American Samoa, according to the NHTSA documents.

Officials from Takata and Toyota could not be reached for immediate comment on the recall.

Dealers will replace the front passenger airbag inflator with a newly made replacement, but if a replacement is not available as a temporary measure the dealer will disable the air bag and advise the customer not to use the front passenger seat, according to the NHTSA documents.

Other automakers affected by the regional recalls include BMW (BMWG.DE), Ford Motor (F.N), Mazda Motor (7261.T), Mitsubishi Motors (7211.T), Nissan Motor (7201.T) and Fuji Heavy Industries' (7270.T) Subaru.

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