Glitches surfaced in the J-Alert system Friday as the government held a test for municipalities deemed at risk from missiles North Korea is threatening to launch toward Guam.

The exercise based on the satellite-based J-Alert system covered 202 municipalities in nine prefectures in the Chugoku and Shikoku regions. It was designed to test municipalities’ ability to receive missile launch alerts and automatically broadcast them to residents.

Last week, North Korea threatened to simultaneously launch four ballistic missiles toward waters near the U.S. territory of Guam, in the western Pacific. The suggested flight path would take the missiles over Shimane, Hiroshima, Ehime and Kochi prefectures.

The drill took place in those four prefectures plus Tottori, Okayama, Yamaguchi, Tokushima and Kagawa.

In the event North Korea launches a missile that might enter Japanese airspace or malfunction over Japanese territory, the J-Alert system will transmit information to towns and cities along the missile’s projected path.

Alerts received from the central government are to be transmitted over outdoor loudspeakers used to issue announcements about natural disasters and to mobile phones and TVs. It might also issue warnings for people to take shelter.

Some of municipalities in Friday’s drill experienced technical glitches with the J-Alert system.

For example, in Yonago, Tottori Prefecture, the loudspeakers didn’t work, and in Okayama, a text message sent by the prefecture ended up being garbled.

In May, the government revised the wording of the J-Alert warnings about missiles in light of developments in North Korea. The warnings now call for people in at-risk areas to take shelter underground or in sturdy buildings.

In light of the North’s latest missile threat, Japan has deployed Patriot Advanced Capability 3 missile interceptor batteries in Shimane, Hiroshima, Ehime and Kochi prefectures.

The Self-Defense Forces have also deployed destroyers in the Sea of Japan armed with Standard Missile-3 interceptors, which are tasked with stopping missiles in the outer atmosphere.