At least 303 motorists died in car accidents after their airbags didn't deploy in now-recalled General Motors vehicles, according to a study released late last night.

The Center for Auto Safety, a non-profit automotive watchdog, reviewed data from the Fatality Analysis Reporting System, and counted deaths involving the Chevrolet Cobalt and Saturn Ion, two vehicles at the heart of several ongoing investigations, to reach its conclusion.

If the airbag non-deployments were the result of a faulty ignition switch that inadvertently turns them off, the death toll would be the largest in automotive history attributed to a single defect, surpassing the 250 deaths investigators linked to defective Firestone Tires more than a decade ago. The rising death toll would further amplify questions about why GM and federal safety regulators at the National Highway Traffic Safety Administration didn't act sooner to correct the problem.

Safety advocates have said both GM and NHTSA failed to act in a timely fashion to alert motorists of the dangers posed by the dangerous defect, of which documents GM had knowledge of as early as 2001 and NHTSA knew about in 2007.

"The question today for NHTSA is how so many ... death reports without an airbag deployment and so many FARS deaths without an airbag deployment failed to trigger an investigation," wrote Clarence Ditlow, the executive director of the Center for Auto Safety. "... For the people who died or were seriously injured in crashes, the answer comes too late."

GM has acknowledged 13 deaths related to the problem, and says the number cited by the Center for Auto Safety study is "speculation."

The review of FARS data, conducted by Friedman Research at the request of the Center for Auto Safety, looked at fatal cases in which airbags did not deploy but did not analyze the causes of the crashes. FARS information is raw data submitted to a national database by state and local authorities when fatal accidents occur.

Last month, GM recalled 1.37 million cars in the U.S. because a faulty ignition switch had been inadvertently moving from the "run" position to the "accessory" position, turning off engines and systems that provide power to airbags.

"Shame is not a strong enough word," said Lou Lombardo, the founder of Care for Crash Victims, another safety-minded nonprofit that advocates for accident victims.

The results of the CAS study were first reported by the New York Times.

Since GM first recalled vehicles in February, the scope of the problem has quickly grown. On Feb. 7, the automaker recalled 619,122 Chevy Cobalts and Pontiac G5s, but then expanded the recall on Feb. 25 to include four more models. At first, the company said GM knew about the problem as early as 2004, but documents released earlier this week indicated the company knew about the defect as early as 2001.

The Department of Justice, a U.S. House of Representatives Subcommittee and NHTSA have already announced investigations into the delays of General Motors' response to the deadly defect.

A spokesperson said Friday morning the conclusions of the Center for Auto Safety's study were premature.

"As knowledgeable observers know, FARS tracks raw data," GM said in a written response. "Without rigorous analysis, it is pure speculation to attempt to draw any meaningful conclusions. In contrast, research is underway at GM and the investigation of the ignition switch recall and the impact of the defective switch is ongoing. While this is happening, we are doing what we can now to ensure our customers' safety and peace of mind."

Pete Bigelow is an associate editor at AOL Autos. He can be reached via email at peter.bigelow@teamaol.com and followed on Twitter @PeterCBigelow.

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