DETROIT >> At least five automakers are teaming up to determine what is causing a problem with air bags used in their vehicles and how many cars to recall because of it.

Inflators used in certain air bags made by the Japanese supplier Takata Corp. can explode with too much force and spew shrapnel into the passenger compartment.

So far, 14 million vehicles worldwide have been recalled due to the problem, including 8 million in the U.S. Takata has yet to pinpoint an exact cause, even though the recalls started a decade ago. The U.S. government wants Takata and automakers to add millions of cars across the U.S. to recalls currently limited to areas with high humidity. The automakers indicated Tuesday that they want to do their own testing, in addition to tests underway at Takata, to confirm the wider recall is necessary.

Toyota and Honda are leading the call for an industrywide investigation. In a statement, Toyota said it will ask the industry to hire an independent engineering company, and the affected companies would share results to figure out recall repairs. So far, Subaru, Chrysler and Ford have agreed to cooperate.

The announcement came as Takata edged closer to a midnight deadline to agree to a national recall of driver’s side air bags or face civil fines and legal action from the National Highway Traffic Safety Administration. The agency said Tuesday that it has yet to receive a response.

Some of the biggest recalls so far have been limited to high-humidity areas in the Southern U.S., plus Hawaii and some territories. The agency has said that prolonged exposure to airborne moisture can cause the inflator propellant to burn faster than designed. That can rupture metal inflator canisters. At least five deaths worldwide have been blamed on the problem.

NHTSA demanded the national recall of driver’s side air bags after receiving reports of two incidents that occurred outside the recall zone. The agency’s demand covers vehicles made by Ford, Honda, Chrysler, Mazda and BMW, generally from the 2008 model year and earlier.

The government says it doesn’t have data to warrant a national recall of passenger side air bags.

In a statement Tuesday, Takata said it had formed a panel to investigate its process for manufacturing inflators, but it didn’t specify whether it would agree to the national recall. Takata also said it’s working with top scientists that specialize in propellants, inflators, and air bag systems to evaluate its inflators.

Takata also appeared to pass the decision about a broader recall to the automakers. The company said it would “produce additional replacement units to support any further recalls that may be announced by our customers.”

A company spokesman said he expects a response to NHTSA later Tuesday.

On Wednesday, Takata and some of the automakers are set to appear at a U.S. House subcommittee hearing on the air bag matter.

Honda, in testimony prepared for the hearing, called its failure to report to the government more than 1,700 death and injury claims due to the air bags “inexcusable.” The company acknowledged recently that it violated federal law in failing to file reports with the National Highway Traffic Safety Administration.

“I know it is difficult to comprehend how, over a 10-year period, we could have 1,729 errors in our early warning reporting,” Honda Executive Vice President Rick Schostek said. “Honestly, it is difficult for me to understand as well.” He said Honda is taking action to make sure it doesn’t happen again.

Marcy Gordon contributed from Washington, D.C.