DETROIT—U.S. auto safety regulators are telling a company that made faulty air bags to manufacture replacement parts faster and do more testing to find out what’s causing the problem.
The National Highway Traffic Safety Administration, under fire for its slow response to safety issues, sent letters to Japanese air bag maker Takata Corp. and 10 automakers seeking information about air bags.
Millions of Takata air bags can potentially inflate with too much force, blowing apart metal canisters and sending shards flying at drivers and passengers. Safety advocates say that four people have died due to the problem.
Tests have shown that prolonged exposure to high humidity can cause the problem. Some automakers have limited their recalls to a small number of high-humidity areas.