Investigators found an ` ` improvised launch device '' outside of Yokota Air Base , officials say . CNN 's Kevin Wang contributed to this report . Residents report hearing two small cannon - like explosions at about 8 am local time . No injuries or signs of violence have been reported , authorities said .
Investigators found an ` ` improvised launch device '' outside of Yokota Air Base , officials say . Residents report hearing two small cannon - like explosions at about 8 am local time . No injuries or signs of violence have been reported , authorities said .