U.S. regulators ordered Honda Motor Co. on Wednesday to provide documents related to its investigation of auto parts maker Takata Corp.'s potentially defective air bags that have prompted over 7 million cars to be recalled in the U.S.

"We are compelling Honda to produce documents and answer questions under oath relevant to our ongoing investigation into defective air bags made by Takata," National Highway Traffic Safety Administration deputy administrator David Friedman said in a statement. "We expect Honda's full cooperation as we work to keep the American public safe."

In the special order addressed to Assistant Vice President Jay Joseph of Honda's U.S. unit, America Honda Motor Co., NHTSA says that while the automaker has agreed to hand over some documents, the U.S. agency needs more to further investigate the issue of Takata's faulty air bags that "may project fragments rather than properly inflating."