Updated

Japan's warning sirens blared when the North Korean missile was launched and again when it passed overhead. TV stations warned people to get inside buildings and go to the basement. Trains and subways on a northern island briefly stopped for safety checks.

If practice makes perfect, people in northern Japan on Friday got another chance to improve on protecting themselves from a future warhead.

It's the second time Japan's emergency alert system kicked into action in less than a month. Ultimately, there was no known debris or damage.

Emergency official Shuji Koshida said the response went relatively smoothly since Hokkaido had the earlier missile flyover on Aug. 29. The warning message was updated after residents said they had trouble finding sturdy buildings to seek refuge the last time.