October 20, 2014 | via sanfrancisco.cbslocal.com

DETROIT (CBS SF/AP) — A potential safety crisis over defective air bags widened Monday as the U.S. government issued an urgent plea to more than 4.7 million people to get their cars fixed.

The inflator mechanisms in the air bags can rupture, causing metal fragments to fly out when the bags are deployed in crashes.

Safety advocates say at least four people have died from the problem and there have been multiple injuries. They also say more than 20 million vehicles in the U.S. are equipped with the faulty air bags.

NHTSA RECALL: Full Background
RECALL LOOKUP: Check If Your Car Has Been Recalled Using VIN Number

The National Highway Traffic Safety Administration warned people whose cars have been recalled during the past two years for faulty air bag inflators to take them to dealers right away. The inflators are made by Takata Corp., a Tokyo-based supplier of seat belts, air bags, steering wheels and other auto parts. So far, automakers have recalled about 12 million vehicles worldwide because of the problem.

“This message comes with urgency,” NHTSA said in a statement. The agency has been investigating the problem since June, and has cited reports of six inflators rupturing, causing three injuries.

The warning covers cars made by Toyota, Honda, Mazda, BMW, Nissan, General Motors and Ford. Passenger or driver air bags or both could be affected depending on the vehicle.

Toyota issued the latest recall Monday, covering passenger air bags in 247,000 older model vehicles including the Lexus SC, Corolla, Matrix, Sequoia and Tundra.

Like many of the other recalls, the Toyota recall covers vehicles in South Florida, along the Gulf Coast, in Puerto Rico, Hawaii, the U.S. Virgin Islands, Guam, Saipan and American Samoa — all areas that have high absolute humidity. Toyota, in documents posted on the NHTSA website, said the company and Takata are still trying to pinpoint the cause of the rupture and to gauge the influence of high absolute humidity.

Absolute humidity is a measurement of water vapor in the air, while relative humidity, which is commonly used in weather reports, measures air moisture content relative to the air temperature.

Toyota has been testing the air bags, and it found an unusually high incidence of inflator failures along the coasts, according to spokesman John Hanson. The investigation continues and the recall could be expanded to more areas, Hanson said.

Toyota says it knows of no crashes or injuries from the cars it has recalled.

Neither Toyota nor NHTSA could say exactly how far inland the recall area goes or what states it covers.

NHTSA urged people to check if their car has been recalled by going to https://vinrcl.safercar.gov/vin and typing in their vehicle identification number.

Clarence Ditlow, executive director of the nonprofit Center for Auto Safety, estimated there are 20 million to 25 million cars in the U.S. alone that are equipped with the faulty air bags.

Toyota said repairs will be done for free and notices will go into the mail starting around Oct. 25, according to documents. People who live in areas that are outside of the recall zone who are afraid of driving their cars should contact their dealerships, Hanson said.

Last week, two U.S. senators questioned why the safety agency is allowing the recalls to be done on a regional basis because cars could be driven to, or people could move to the high-humidity states.

They also cited the May 27, 2009, death of 18-year-old Ashley Parham of Oklahoma City. She was driving a 2001 Honda Accord across a high school parking lot in Midwest City, Oklahoma, when it hit another car. The air bag inflated and sent shards of metal into her neck, causing her death.

“Based on NHTSA’s open investigation, the agency will take appropriate action, including expanding the scope of the recall if warranted,” an agency statement said.

Takata has said it recognizes the critical role that government plays in public safety, and it is supporting safety regulators.