(Adds Takata response to lawmaker's comments, more details from Senate committee report.)
By David Shepardson and Paul Lienert
WASHINGTON/DETROIT, Feb 23 (Reuters) - U.S. lawmakers on Tuesday stepped up pressure on federal regulators and Takata Corp to accelerate the recall of millions of airbag inflators, citing evidence that the Japanese company manipulated data to cover up problems with its products.
In another development on Tuesday, a group of 10 automakers said the cause of Takata airbag ruptures linked to 10 deaths and more than 100 injuries is a combination of exposure to humidity, design and manufacturing issues, and use of the volatile chemical ammonium nitrate.
Reuters reported on Monday that the National Highway Traffic Safety Administration (NHTSA) continues to investigate whether the recalls of nearly 29 million defective Takata inflators in the United States should be expanded to include another 70 million to 90 million inflators with ammonium nitrate.
A Senate Commerce, Science and Transportation committee report cited a series of internal Takata documents generated over the past 12 years that showed company officials argued data on inflator quality and testing was manipulated to disguise problems. A redacted 2013 document released by the committee indicates an unidentified Takata manager told the company's senior vice president of quality assurance that proposed limitations to the scope of a 2013 airbag recall might be "a violation of our moral obligation to protect the public."
U.S. Senator Bill Nelson cited the Monday Reuters report on the Senate floor, and said it was "puzzling" that NHTSA has allowed Takata to continue production of ammonium nitrate-based inflators 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 the Florida Democrat, reiterating calls by senators for action on the issue.
The current recall may have to be redone, Nelson said, "because auto manufacturers are installing new live grenades into people's cars as replacements for the old live grenades."
Takata spokesoman Jared Levy said issues about testing and data handling raised by Nelson and a Democratic staff report "are entirely inexcusable and will not be tolerated or repeated."
"Issues with validation testing of the original phase stabilized ammonium nitrate inflators are not the root cause of the field ruptures...but these issues are totally incompatible with Takata's engineering standards and protocols," Levy said.