Federal highway regulators dramatically expanded the number of vehicles subject to the recall of Takata airbag inflators this week.
The National Highway Traffic Safety Administration previously recalled nearly 29 million inflators, which are blamed for at least 10 deaths in the U.S.
The agency announced Wednesday that the recall order would be expanded to include all Takata inflators that use ammonium nitrate propellant without a drying agent. Research showed that the propellant can degrade under hot and humid conditions, which could lead to the inflator exploding and sending shrapnel into vehicle interiors.
The recall, which the NHTSA called "the largest and most complex safety recall in U.S. history," is expected to affect another 35 million to 40 million inflators through 2019.
NHTSA Administrator Mark Rosekind noted that the most dangerous Takata inflators are already subject to recall and that the expansion will replace additional inflators before they become dangerous.
The recall will be issued to highest-risk vehicles first after the agency unveils the expanded order this summer. The NHTSA plans to consult with automakers to implement the expansion to ensure "a 100 percent recall completion rate."
"Everyone plays a role in making sure that this recall is completed quickly and safely, including manufacturers, suppliers and vehicle owners themselves," Rosekind said in a statement.
The revised order will also require Takata to direct its research toward the safety of inflators that utilize a chemical drying agent. Those inflators could be added to the recall in the future unless the company definitively proves their safety.
Prior to the expanded order, U.S. officials estimated that some 85 million Takata inflators remained on the road.
"The acceleration of this recall is based on scientific evidence and will protect all Americans from air bag inflators that may become unsafe," added Transportation Secretary Anthony Foxx.
Takata, meanwhile, is reportedly in talks with companies in an effort to secure financial assistance in the wake of the airbag inflator crisis. The company estimated that previously announced recalls could cost $3.5 billion — an amount well in excess of its $1.3 billion in assets as of December.