Most at risk are motorists who have had their airbags replaced over the past three years by a repair shop other than a new car dealership, the National Highway Traffic Safety Administration officials said.
Only 0.1 percent of the U.S. vehicle fleet - about 250,000 cars on the road - are makes and models for which counterfeit airbags are known to be available, NHTSA said. Auto industry officials briefed by the agency said they were told that tens of thousands of car owners may be driving vehicles with counterfeit airbags.
In government tests last month of 11 counterfeit bags, 10 didn't inflate or failed to inflate properly. In one test, a counterfeit bag shot flames and shards of metal shrapnel at a crash dummy instead of inflating, said NHTSA Administrator David Strickland, who showed a video of the test at a news conference.
"It is an extreme safety risk," he said.
NHTSA is asking car owners to check a government website, www.Safercar.gov, for information on how to contact auto manufacturer call centers to learn if their vehicle model is among those for which counterfeit airbags are known to have been made.
No deaths or injuries have been tied to the counterfeit bags, NHTSA said. But it's unclear whether police accident investigators would be able to identify a counterfeit bag from a genuine one, industry officials said.
About 1.5 million airbags are deployed each year in police-reported tow-away crashes, Clarence Ditlow, executive director of the Center for Auto Safety, said.
"Airbags save several thousands of lives annually. But they can't save lives if they have not been repaired properly," he said.
NHTSA has compiled a list of dozens of vehicle makes and models for which counterfeit airbags may be available, but the agency cautioned that the full scope of the problem isn't clear yet and the list is expected to "evolve over time."
If a car model is on the list and has had its airbags replaced during the past three years by a repair shop other than a new car dealership, NHTSA is asking owners to take the vehicle into a dealership or repair shop to be inspected at their own expense to determine whether the replaced airbags are counterfeit.
Fees for checking out airbags - a complex and technical process - could run between $100 to $200, said Bailey Wood, a spokesman for the National Automobile Dealers Association, said. The cost of replacing a driver's side center column airbag is $750 to $100, he said. Other airbags may be more, he said. Some types of cars have as many as eight airbags.
The problem isn't the result of a manufacturing defect by automakers and isn't a recall, NHTSA and industry officials said.
"The bad actor here is the counterfeiters," Wood said. "Because of that, the cost to have an airbag evaluated and possibly replaced is going to be borne by the consumer."
The counterfeit bags typically look like airbags made by automakers and usually include a manufacturer's logo. Government investigators believe many of the bags come from China, an industry official said.
The bags are marketed to auto repair and body shops as the real deal, industry officials said. Auto dealerships that operate their own body shops are usually required by their franchise agreements to buy their parts, including airbags, directly from automakers and therefore are unlikely to have installed counterfeit bags, industry officials said.
But only 37 percent of auto dealers have their own body shops, according to the automobile dealers association. Many consumers whose vehicles have been damaged are referred by their insurance companies to auto body shops that aren't affiliated with an automaker.
Consumers who bought replacement airbags online or who have purchased a used car that may have its airbags replaced in the past three years were also asked to check NHTSA's list.
Counterfeiting of a wide variety of auto parts has long been a well-known problem, industry officials said. But recent incidents have escalated concern by government officials. In August, federal agents confiscated nearly 1,600 counterfeit airbags and arrested a North Carolina auto mechanic, according to a report by the Charlotte Observer. The mechanic was tied by federal officials to another counterfeit airbag case last year in Tennessee, the report said.
Dai Zhensong, a Chinese citizen, pleaded guilty and was sentenced in federal court in Chattanooga, Tenn., last February to 37 months in prison for trafficking in counterfeit airbags, according to a statement made at the time by the U.S. Attorney's Office.
Zhensong was a part owner and manager of the international department of Guangzhou Auto Parts, which made a variety of auto parts, many of which were counterfeit, the statement said. In 2010, he traveled from China to Chattanooga to sell additional counterfeit airbags and other auto parts.
The counterfeit airbags were manufactured by purchasing genuine auto airbags that were torn down and used to make molds to produce the counterfeit bags. Trademark emblems were purchased through Honda, Toyota, Audi, BMW and other dealerships located in China and affixed to the counterfeit airbags. The airbags were advertised on the Guangzhou Auto Parts website and sold for approximately $50 to $70 each, far below the value of an authentic airbag, the statement said.
About 2,500 counterfeit airbags have been seized by law enforcement authorities so far this year, John Morton, director of U.S. Immigration and Customs Enforcement, told reporters. Investigations are under way in several locations around the country, and further arrests and seizures are expected, he said.