DETROIT (AP) — U.S. safety regulators are warning owners of more than 4.7 million vehicles that have been recalled for air bag problems to get them repaired immediately.

The warning issued Monday by the National Highway Traffic Safety Administration covers vehicles from multiple manufacturers that date to 2002.

Inflators can rupture in air bags made by Takata Corp., causing metal fragments to fly out when the bags are inflated in crashes. So far, automakers have recalled about 12 million vehicles worldwide because of the problem.

Safety advocates estimate that more than 20 million cars have the faulty inflators in the U.S. alone. They say at least four people have died from the problem.

The inflators have led to multiple recalls from Honda, Toyota, Nissan, Mazda, General Motors, Ford, Chrysler, BMW and Mitsubishi.