With 16 million vehicles recalled, a number of lawsuits and several investigations already underway related to defective Takata-produced airbags, lawmakers are urging the Department of Justice to open a criminal investigation into the Japanese auto parts maker following revelations that the company knew off issues four years prior to the first recall.

The New York Times reports that Takata began secret tests of its airbags back in 2004 after receiving a report that one of its devices had ruptured, shooting metal fragments at an Alabama driver.

Two former employees involved in the tests, one of whom was a senior member of the testing lab, tell the Times that the test were performed after normal working hours an on weekend at the company’s American headquarters in Michigan.

During the course of the testing, which involved 50 airbags recovered from scrapyards, two airbags cracked creating a condition that can lead to rupture.

The two airbags in question reportedly showed cracks and the start of “rapid disassembly,” the term used by Takata for explosion.

According to one of the former employees the results were enough to spur engineers to immediately begin looking for possible fixes in preparation for a recall.

One of the employees says engineers at the time thought the problem lied within the welding of the inflater’s canister, the area used to hold the airbag’s explosives. To counter the issue engineers reportedly designed prototypes for possible fixes, but their work was halted about three months later.

The former employees say that executives didn’t believe there was significant risk and allegedly ordered lab technicians to delete the testing data and dispose of the inflaters in the trash.

The Times reports that the two airbags that had shown issues were discounted by officials at the company because they were retrieved from cars with cracks in the windshields. The employees say executives, including Takata vice president of engineering Al Bernat, considered the airbags “corrupted by weather.”

When contacted by the Times, Bernat declined to comment and referred questions to his former employer. Takata also declined to comment.

The former employees say they brought the information forward because of concerns that Takata was not being forthright about the defective airbags.

“All the testing was hush-hush,” one former employee tells the Times. “Then one day, it was, ‘Pack it all up, shut the whole thing down.’ It was not standard procedure.”

It wasn’t until four years after the testing occurred that the first recall involving Takata airbags was initiated.

Since then 16 million vehicles from 10 different car manufactures have been recalled over concerns that the airbags could rupture shooting shrapnel at passengers. So far the airbags are believed to be responsible for at least four deaths and 139 injuries.

While a spokesperson for Takata declined to comment on the new allegations, a spokesperson for Honda, the company’s biggest customer, tells the Times that the company plans to “determine whether anyone at Honda has any evidence that these claims are credible.”

According to the Times, the accounts from the former Takata testing employees in Michigan highlight other quality issues recalled by employees at the company’s Texas distribution center.

Those employees, along with emails, photos, videos and regulatory filings viewed by the Times cast doubt on the company’s handling of airbags in the early 2000s.

The Times reports that emails show workers raising concerns that airbag units were being delivered to automakers wet or damaged because of transportation mishaps.

As Consumerist reported previously, investigators believe that moisture can render the volatile chemicals used in Takata airbags to be unstable, creating an environment where too much force is present during deployment.

“The whole situation makes me sick,” one manager wrote in a February 2007 email addressed to multiple colleagues. The email reportedly goes on to complain that measures the center had introduced to try to keep the airbags dry were being ignored.

Additionally, the Times reports that closed circuit television footage shows forklifts dropping the airbags. The employees claim those safety devices were never inspected for damage.

Takata’s own guidelines from 2009 stressed the importance of dangers related to mishandling the airbags, including a link to a video that shows side-curtain airbags deploying, shooting the inflater into the car’s cabin, the Times reports.

A 2005 email from a manager to employees further warned of issues the airbags could have if mishandled.

“The propellant arrangement inside is what can be damaged when the airbags are dropped,” that manager wrote. “Here you can see why it is important to handle our product properly.”

Employees of the Texas facility say that many of the warnings were disregarded because of the company’s need to quickly turnout airbags.

The National Highway Traffic Safety Administration recently opened an investigation into Takata’s airbags, but some lawmakers say that isn’t enough.

Senators Richard Blumenthal of Connecticut and Ed Markey of Massachusetts called on the Department of Justice to open a criminal investigation into Takata after news of the secret testing was revealed.

“Reports that Takata concealed and destroyed test results revealing fatal air bag defects, along with other evidence that the company was aware of these deadly problems, clearly require a criminal investigation by the Department of Justice,” Blumenthal and Markey say in a news release. “If the reports are true, the company must be held accountable for the horrific deaths and injuries that its wrongdoing caused. These allegations are credible and shocking — plainly warranting a prompt and aggressive criminal probe.”

Takata Saw and Hid Risk in Airbags in 2004, Former Workers Say [The New York Times]

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