Lawmakers in the U.S. increased the pressure on Takata Corp. and federal regulators on Tuesday, to hasten the process of the recall of several million airbag inflators.

The lawmakers have cited evidence and claim that the Japan-based company intentionally manipulated and faked the test results to cover up the exploding airbag issue.

Moreover, 10 automakers have come forward and revealed on Tuesday that the reason behind the airbag ruptures – which led to more than 100 injuries and 10 deaths – is a combination of factors namely: humidity, use of the volatile chemical ammonium nitrate and issues with design and manufacturing.

The National Highway Traffic Safety Administration (NHTSA) is continuing to investigate the matter and considering if the recall of nearly 29 million defective airbag inflators from the company in the U.S. should be extended to include an additional 70 to 90 million inflators that had ammonium nitrate.

A report [pdf] from the Senate Commerce, Science and Transportation committee cites internal documents from Takata in the past 12 years, which revealed that company officials debated over the data pertaining to the quality and testing of the inflator was manipulated to cover the issues.

A redacted document from 2013 that the committee released suggested that an unidentified Takata manager told the company's SVP that the intended limitations to the 2013 airbag recall's scope could be "a violation of our moral obligation to protect the public."

Bill Nelson, the U.S. Senator, said that it is indeed "puzzling" that the NHTSA has let Takata Corp. continue the production of the questionable inflators which are ammonium nitrate-based indefinitely.

"Why aren't they taking a more aggressive approach? And what's going on after all of these inflators, based on what we see with ammonium nitrate, have been exploding?" asked Nelson, calling for immediate action.

On Tuesday, the NHTSA stated that a consent order was issued in November 2015 to the company under which "all Takata ammonium nitrate-based inflators must eventually be recalled unless Takata can establish their long-term safety."

The concerns pertaining to the safety of ammonium nitrate's use as a propellant continue to linger. The NHTSA has given the Japanese company time until 2019 to substantiate that the recent propellant formulations it uses in its airbags are safe.