U.S. Transportation Secretary Anthony Foxx said Friday that the world’s largest air-bag maker, Takata, will be fined $14,000 a day until it complies with federal demands for more information on air bags that have killed six people and maimed dozens more.

“Those air bags can explode with such force that they have grievously injured people and, in a half-dozen cases­, killed them,” Foxx said. “To remove that threat and get to the root cause of this defect, we need Takata’s cooperation, and so far they have not demonstrated it.”

The metal inflation canisters on some Takata air bags have been shattered by the propellent they contain, spraying drivers and passengers with shards of metal. More that 22 million vehicles, including about 17 million in the United States, have been recalled by automakers. Only 2 million U.S. vehicles had been repaired as of December.

“We’ve pushed hard to get millions of defective Takata air bags off our roads,” said Foxx, who was in Richmond on a bus tour to promote infrastructure investment. The National Highway Traffic Administration “has issued two orders compelling Takata to provide the documents and information we need to fix this problem, and the company has failed to abide by those orders. Takata’s failure to fully cooperate with our investigation is unacceptable and will not be tolerated.”

Foxx also asked Congress to require that rental cars and used cars up for sale that are under recall be repaired before they are rented or sold. The most recent death attributed to a Takata air bag, that of Carlos Solis, 35, near Houston last month, came in a used car that was under recall when he bought it, NHTSA said.

Although it was first threatened with the fines in November, Takata issued a statement Friday saying it was “surprised and disappointed.”

“We strongly disagree with their characterization that we have not been fully cooperating with them,” the statement said. “We have provided the agency with almost 2.5 million pages of documents to date. We have also been meeting regularly with NHTSA engineers on efforts to identify the root cause of the inflator issue.”

NHTSA, in a letter sent to the Japanese company Friday, said that “Takata is neither being forthcoming with the information that it is legally obligated to supply, nor is it being cooperative.”

“Takata has failed to provide the information we need to properly analyze the 2.4 million documents it has produced,” NHTSA spokesman Gordon Trowbridge said in a conference call with reporters.

Trowbridge said NHTSA was preparing a preservation order that would require Takata to maintain and provide all of its internal test results. He pointed car owners to the federal Web site safercar.gov, where they can enter their vehicle identification number to see if it has been subject to recall.

“If they receive a notice, make an appointment to immediately have that vehicle repaired,” Trowbridge said.

Faced with dozens of proposed class-action lawsuits in the United States that also may name many of their automaker customers, Takata has moved cautiously when pressed to identify the cause of the deadly air-bag deployments or acknowledge its fault.

Ten auto manufacturers — Toyota, Honda, Mazda, Mitsubishi, General Motors, Subaru, Ford, Chrysler, BMW and Nissan — have issued air-bag recalls since the problem emerged more than six years ago.

Regulators first thought — and Takata still believes — that the inflator explosions were caused by sustained exposure to humidity and heat. The initial U.S. recalls were in southern regions, where the five U.S. fatalities and most of the injuries occurred. But last year, NHTSA demanded that the recall be nationwide.

Takata said Friday that its research “so far, supported our initial view that age and sustained exposure to heat and humidity is a common factor in the small number of inflators that have malfunctioned.”

NHTSA believes that the inflator propellant used by Takata, ammonium nitrate, burns faster than intended after exposure to prolonged moisture in the air. A fast burn can cause an explosion of the metal canister that is supposed to contain the explosion.