The National Highway Traffic Safety Administration is resisting pleas to further expand the Takata safety recalls to include all of the automotive supplier’s air bag inflators that contain an ammonium nitrate propellant.

Senator Bill Nelson (D-Fla.), a minority member of the Senate Commerce Committee, on Feb. 23 called on NHTSA to expand the recalls yet again, citing new evidence that Takata falsified inflator testing results as far back as 2004. Takata handed over thousands of documents and emails to the committee as part of an investigation, and some of them reference the fudging of validation testing data to mislead automaker clients.

The documents and emails are included in a report released by the committee's minority staff.

“These new documents speak for themselves,” Nelson said. “There is no doubt in my mind that Takata failed to prioritize the safety of its products.”

Nelson’s requested recall expansion would add up to 90 million more air bag inflators, he said.

But in a letter dated Feb. 26, NHTSA Administrator Mark Rosekind rebuffed Nelson’s suggestion, arguing that such an expansion wouldn’t improve public safety and would further complicate the task of providing replacement air bag inflators for vehicles already under recall. Current Takata recalls affect about 28 million vehicles built by 14 different manufacturers that used Takata as a supplier.

As of Feb. 12, 4.1 million driver-side air bags and 3 million passenger-side air bags have been repaired as part of the recalls, according to NHTSA.

A consortium of 10 automakers, called the Independent Testing Coalition, identified three factors as the root cause of the deadly air bag inflator ruptures: the use of ammonium nitrate, flaws in the construction of Takata’s inflator assembly, and exposure to heat and humidity. The group’s work isn’t finished, however. It’s now investigating the performance of Takata’s replacement inflators, the safety level of Takata’s more recent formulations of ammonium nitrate propellant that use a desiccant additive to combat moisture, and the safety performance differences between passenger- and driver-side inflators.

To view an updated list of vehicles included in the Takata recalls, click here.