According to three insiders speaking to Bloomberg under the condition of anonymity, Takata changed the recipe of its inflator propellant in 2008 to lower the risk of rupture after long periods of exposure to humidity. The decision came in the wake of Honda's decision that year to recall the flawed parts. Since then, some government officials have been advised about this switch.
Additionally, Takata has released some of its own evaluations to NHTSA. After activating 30,801 inflators in testing, it found 265 that ruptured, according to Automotive News. These parts had been removed from recalled vehicles.
The supplier also has 84 reports of rupturing inflators on the road, including 15 of those in models that weren't recalled. According to Automotive News, 63 of those cases were on the driver's side and 21 on the passenger side.
NHTSA's announcement yesterday said that it didn't yet know "a definitive root cause" for the ruptures. However, exposure to moisture appears to be part of the problem because it causes the propellant in the inflator to ignite too quickly. The faulty parts have been linked to six deaths worldwide, and a US District Court in Florida has been evaluating dozens of lawsuits over fatalities and injuries related to the problem.