The 2003 Toyota Corolla is one of about 20 models covered by the latest recall related to defective Takata airbags.

With Toyota not only expanding a recall due to defective airbags but also bringing back some vehicles it had previously repaired, U.S. safety regulators have launched an investigation into the airbags produced by Japanese supplier Takata – a move that could impact not only Toyota but a number of other major manufacturers.

Credited with saving thousands of lives, airbags have also been implicated in a number of recent recalls and even blamed for causing some deaths and injuries. And industry observers caution that with the number of airbags found in the typical vehicle rising, the problem could become worse in the years ahead.

Many, but not all, of the most recent problems have centered around the so-called supplementary inflatable restraints produced by Takata. The new investigation by the National Highway Traffic Safety Administration focuses on approximately 1.1 million vehicles sold by Toyota, Nissan, Chrysler, Honda and Mazda. Defective inflators could cause fires or even send debris shooting into the passenger compartment like shrapnel.

At least six reports have been recorded by NHTSA involving inflator problems in vehicles sold during the 2002 to 2006 model-years.

(Toyota expands earlier airbag recall. Click Here for the full story.)

Several of the makers targeted by the new investigation have indicated plans to work with government investigators on resolving the problem. But a report by the Detroit News indicate the inflators may have been manufactured improperly at a plant in Washington state. It is also possible parts for the inflators were exposed to moisture before final assembly at another plant in Mexico.

Last year, Takata airbags were the source of recalls involving 3.7 million vehicles worldwide, a move involving six different automakers. But that now appears to have only partially addressed the problem.

(No more major safety problems, promises GM CEO Barra. Click Here for more.)

It turns out the partsmaker failed to provide full information to its customers and earlier this week, Toyota was forced to add another 650,000 more vehicles to the 2.3 million it recalled in 2013.  Worse, Toyota said it would have to “re-notify” some owners covered by the earlier recall because repairs might not have been made properly.

In a statement, NHTSA said, “At this time, NHTSA has not seen a defect trend across other vehicles involving the use of switchblade keys. The agency is in contact with automotive manufacturers and suppliers regarding airbag design and performance related to the position of the vehicle ignition switch and will take appropriate action based on the agency’s findings.”

But the problems with Takata airbags are not unique. In fact, airbags have been linked to a variety of issues in recent years.  In many cases, the problems center around the airbags themselves, with issues such as faulty inflators causing them to improperly operate in a crash. But in other recalls, the focus has been on issues such as faulty installation.

(Study cites pattern of “incompetence and neglect” at GM. Click Here for more.)

Hyundai, for example, was forced to recall nearly 200,000 Elantra models in 2013 after receiving complaints that a support bracket could become displaced in the event of a crash that triggers the side-impact airbags. NHTSA was first alerted to the problem when a passenger had serious lacerations to their ear during a crash.

Even before the big Takata recalls in the spring of last year, Honda and Toyota had already announced service actions involving 1.5 million vehicles due to airbag problems. In 2012, there were 22 separate recalls involving 18 different makers due to airbag problems, according to federal data.

The airbag problems of recent years have loosely fallen into three categories:

• Airbag systems that deploy when they’re not needed, whether due to faulty sensor or short-circuiting control systems, or because of incorrectly programmed software;
• Airbags that fail to deploy for similar reasons;
• Airbags that may not be properly installed and can inflate too aggressively or even send shards of plastic or metal flying into the passenger compartment like shrapnel from a bomb.

A separate problem came to light when, in October 2012, NHTSA announced that millions of vehicles may have been fitted with counterfeit – and potentially faulty – airbags after crashes that caused their original airbags to deploy.

Industry analysts caution that airbag problems could continue to grow as manufacturers add even more of the devices to their vehicles. Today, some products may be equipped with 10 or more of the safety devices. They can be lifesavers when they work properly. But in rare situations, airbags can actually make a dangerous situation even worse, observers warn.