Company president Koji Sato said Toyota is attempting to determine how its supply chain would be affectedafter suppliers Sumitomo Electric and Aisin suffered damage during the quake.
The bolts designed to keep the plug from moving off the spots were missing, said NTSB investigators, who are trying to determine if the equipment was ever installed.
Some potential targets of the coalition's attacks could include launchers for anti-ship missiles and drones, as well as storage facilities for ammunition.
The shutdown comes about a week after Daihatsu said it was suspending all vehicle shipments after it was found that the organization used improper testing for 64 vehicle models.