More than 650 Takata airbags exploded during tests after they were pulled from vehicles that were part of the recall.

New testing results revealed that more than 650 Takata-produced airbag inflators ruptured after being pulled from vehicles as part of the largest recall in automotive history.

According to documents released by the National Highway Traffic Safety Administration last week, 660 inflators pulled from 245,000 vehicles ruptured when undergoing additional testing. The inflators have been linked to as many as 15 deaths globally and more than 100 serious injuries.

The recalls are being performed in waves with the oldest vehicles involved being part of the first round of replacements. The inflators degrade over time so older vehicles get priority in the recall.

“You have to start where you see the highest risk,” said Jared Levy, a spokesman for Sard Verbinnen & Co., told Bloomberg News.

The test results were revealed in regular reports that the Japanese supplier must file as part of the consent order it agreed to last year.

(Takata CEO outlines plans to resign. For more, Click Here.)

The Takata problem appears to have been triggered by a manufacturing defect that makes its older airbag inflator design especially vulnerable to high heat and humidity. But a recent, industry-funded study also warned that the basic chemical used in the inflators, ammonium nitrate, is vulnerable to breaking down and misfiring as it ages.

If it malfunctions, an inflator can cause plastic and metal shrapnel to spew into the passenger compartment, something that has so far led to at least 10 deaths in the U.S. alone.

The bags rupture primarily for two reasons, according to the reports: materials and manufacturing problems. With time and exposure to moisture and changing temperatures can make the ammonium nitrate unstable.

“We extend our sincerest apologies to those who have been affected by the inflator failures,” the company said in a statement emailed to Bloomberg.

(Eight automakers announce recall of another 12 mil. Takata airbags. Click Here for the latest.)

“As outlined in the report delivered to NHTSA, Takata has focused extensive resources on researching and testing of airbag inflators, including working with independent, world-class technical experts to identify the causes of the inflator failures as they arose and taking action based on the best available understanding.”

Takata has been struggling to supply enough new airbag inflators to replace those under recall, and its cash crunch has made it difficult to ramp up production.

According to reports from Japan, CEO Takada announced his plan to step down during the partsmaker’s annual shareholder meeting.

“I don’t intend to hold on to my position,” Takada said during the meeting. “Once I’ve delivered this company to a place where it’s not at risk of faltering, I want to pass the baton.”

(To see more about Takata selling off ownership stakes in automakers to raise money for compensation, Click Here.)

NHTSA said the recall, initially focusing on older vehicles operating in high humidity regions, such as Southern Florida, is expected to complete by 2019.