TOM KRISHER

Associated Press

DETROIT -- U.S. auto safety regulators have backed away from seeking a giant recall of nearly 50 million air bag inflators and will investigate further after the auto industry raised questions about whether all of the inflators are defective.

The move by the National Highway Traffic Safety Administration is vastly different from a decision reiterated by the agency in July that the inflators made by ARC Automotive Inc. of Tennessee are defective, dangerous and should be recalled.

The agency said inflators in about 49 million vehicles from 13 manufacturers are at risk of exploding and hurling shrapnel into drivers and passengers. They're responsible for at least seven injuries and two deaths in the U.S. and Canada since 2009, and recalling all of them would have cost millions of dollars.

But in a document posted Wednesday in the Federal Register and dated Dec. 13, the agency said it considered comments on a decision from July seeking the recall. The auto industry pointed to technical and engineering differences between ARC inflators in vehicles made by different manufacturers. The comments also raised manufacturing-process variations at different plants that made the ARC inflators.

"Given the potential relevance of these issues to the agency's decision making, including the appropriate scope of any recall, further investigation is warranted," the agency said in the document.

A message was left seeking comment from ARC, which is owned by by Yinyi Group of China.

NHTSA said that it carefully considered the comments on its decision to seek a recall of all the inflators and decided that more investigation is warranted.