The U.S. government is telling 3 million more car owners to get their air bags repaired immediately, but its message has generated some confusion about which cars are actually affected.

The government’s auto safety agency is now warning 7.8 million car owners that inflator mechanisms in the air bags can rupture, causing metal fragments to fly out when the bags are deployed. The original warning Monday covered 4.7 million vehicles.

Safety advocates say at least four people have died from the problem, which they claim could affect more than 20 million cars nationwide. The inflators are made by Japanese parts supplier Takata Corp.

Car owners might experience some uncertainty, however, in determining if their vehicle is equipped with the potentially dangerous air bags. The warnings from the National Highway Traffic Safety Administration cover certain models made by BMW, Chrysler, Ford, General Motors, Mazda, Honda, Mitsubishi, Nissan, Subaru and Toyota.

Most of the 7.8 million vehicles are subject to existing recalls. But manufacturers have limited the recalls to high-humidity areas, excluding cars and trucks in states to the North. NHTSA says owners in Florida, Puerto Rico, Guam, Saipan, American Samoa, the U.S. Virgin Islands, Hawaii and “limited areas near the Gulf of Mexico in Texas, Alabama, Mississippi, Georgia, and Louisiana” should pay special attention to the warning.

Worse yet, the regulatory agency has twice corrected the number of vehicles affected and admitted that a list it released Monday included some cars not equipped with Takata air bags while omitting others that have them. The agency urged people to use its website see if their cars are affected — but a feature allowing people to check for recalls by vehicle identification number malfunctioned Tuesday and still wasn’t operational Wednesday morning.

Automakers have been recalling cars to fix the problem for several years, but neither Takata nor NHTSA have identified a firm cause. The agency opened a formal investigation into the problem in June, and agency documents detail a theory that the chemical used to inflate the air bags can be altered by high humidity, making it explode with too much force while deploying.

“It’s in a total state of uproar right now,” said Clarence Ditlow, executive director of the Center for Auto Safety, a nonprofit advocacy group founded by Ralph Nader.

NHTSA Deputy Administrator David Friedman said in a statement that responding to the recalls is essential to keep people safe.

“It will aid in our ongoing investigation into Takata air bags and what appears to be a problem related to extended exposure to consistently high humidity and temperatures,” he said. The agency, he said, is tracking down the “full geographic scope” of the issue.

The rare warning by regulators comes three weeks after a Sept. 29 crash near Orlando, Florida, that claimed the life Hien Thi Tran, who suffered severe neck wounds that investigators said could have been caused by metal fragments flying out of the air bag on her 2001 Honda Accord. Her Accord was among the models being recalled.

One police agency concluded that the air bags caused her wounds, while another is still investigating. NHTSA is seeking information in the case.

On Monday, Toyota issued a recall covering passenger air bags in 247,000 older model vehicles including the Lexus SC, Corolla, Matrix, Sequoia and Tundra. Like many earlier recalls, Toyota’s 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 said it’s working with Takata to pinpoint the cause of the rupture and to gauge the influence of high absolute humidity, which is a measurement of water vapor in the air.

(AP)