Shares of Takata Corp opened down 1 percent on Friday after the Japanese auto parts maker said it was the subject of a U.S. criminal investigation over defective air bags that have been linked to five deaths.

A Takata spokeswoman said on Thursday a federal grand jury had subpoenaed Takata's U.S. unit to produce documents on the air bag defects. An investigation by U.S. prosecutors in Manhattan had been previously reported but Thursday's statement is the first indication that a seated grand jury was seeking evidence.

The U.S. Senate commerce committee has separately scheduled a hearing next Thursday to solicit testimony from Takata executives on the air bag defects.

Takata's shares were down 1.3 percent at 1,215 yen in early trade, against a slight rise in the broader Tokyo market.