The U.S. National Highway Traffic Safety Administration added about 3 million vehicles to its tally of cars recalled to replace defective Takata Corp. air bags, one day after urging owners to take immediate action.

The auto safety regulator said 7.8 million vehicles are involved in 2013 and 2014 recalls tied to Takata air bags, according to a statement on its website. The Washington-based agency added callbacks by automakers including Ford Motor Co. that weren’t included in a statement released Tuesday.

Takata is under rising scrutiny amid escalating global recalls related to its faulty air bags, with Honda Motor Co., its largest customer, calling back more than 6 million vehicles since 2008. NHTSA advised particular urgency in high-humidity and warm regions, where the air bags may be prone to exploding and propelling metal shrapnel at passengers.

Takata fell as much as 3.6 percent to 1,625 yen in Tokyo trading, erasing earlier gains after NHTSA updated its tally. The Tokyo-based company plunged 23 percent Tuesday, its steepest one-day drop since its 2006 listing, and traded at 1,700 yen, up about 1 percent, as of 11:05 a.m. in Tokyo.