Beleaguered airbag maker Takata will recall a further 35 to 40 million inflators in the United States, the US National Highway Traffic Safety Administration (NHTSA) said Wednesday.
The airbags made by the Japanese supplier can reportedly rupture explosively in a collision, spraying metal fragments at drivers and passengers.
Combined with the 28.8 million Takata inflators already under recall because of links to deaths and injuries, the action amounts to the largest and most complex recall in US history, NHTSA head Mark Rosekind said.
Takata said it was not aware of any ruptures in the inflators targeted in the latest recall, nor of any scientific evidence of any serious associated risk, Japan's Jiji Press reported, citing unnamed sources in the company's US office.
Rosekind said the issue was "urgent," and he implored all car owners to take action immediately if their vehicle appeared on the recall list.
The agency acted after confirming the root cause of the ruptures - a combination of age of the airbag, environmental moisture and high temperature fluctuations that cause the inflators' ammonium nitrate propellent to degrade.
"This degradation can cause the propellant to burn too quickly, which creates too much pressure, and can rupture the inflator module and send dangerous shrapnel through the air bag and potentially injuring or killing vehicle occupants," Rosekind said.
“The science now clearly shows that these inflators become unsafe over time, faster when exposed to high humidity and variations of temperature,” he said, adding that a phased recall schedule will address the inflators before they become dangerous.
The expanded recall will take place in five phases beginning this month and extending to December 2019.
"Today’s action is a significant step in the US Department of Transportation’s aggressive oversight of Takata on behalf of drivers and passengers across America,” US Transportation Secretary Anthony Foxx said in a statement.
"The acceleration of this recall is based on scientific evidence and will protect all Americans from air bag inflators that may become unsafe," Foxx said.
Honda disclosed Wednesday two people died in Malaysia when their Takata-made airbags ruptured in two separate incidents in April and May. The cars involved - a 2003- and 2006-model Honda City - had been under recall.
These are the second and third deaths involving faulty Takata airbags in Malaysia. Thirteen deaths and many injuries have now been linked to the defect worldwide. In the US alone, 10 deaths have been reported - the latest on March 31 - and hundreds of injuries, according to NHTSA.
Carmakers have recalled more than 50 million vehicles with Takata airbags globally since 2008. The recalls have hit profits at firms including Honda and Mazda.
Japanese media reported in late April that a major further recall by the US was thought to be imminent.