Two U.S. senators are calling on U.S. auto safety regulators to immediately issue a nationwide recall for cars with faulty air bags made by Takata Corp.

Sens. Richard Blumenthal of Connecticut and Edward Markey of Massachusetts made the call in a letter to Transportation Secretary Anthony Foxx, who oversees the National Highway Traffic Safety Administration.

The letter delivered Thursday also asks Foxx to encourage automakers to provide free loaner cars if parts aren’t available.

Air bag inflators made by Takata can rupture, causing metal fragments to fly out in a crash. Safety advocates say the problem has caused four deaths. So far automakers have recalled about 12 million vehicles worldwide due to the problem.

But in the U.S. many automakers have limited the recall to high-humidity areas in southern states.

(AP)