Seven Chinese citizens were arrested on charges of illegally entering Guam around the time the U.S. Missile Defense Agency conducted a key missile interception test using a new radar, the island’s Customs and Quarantine Agency has said.

The agency said at least four of the people arrested on Dec. 10-11 were found “in the vicinity of a military installation”. Guam has many such installations, including Andersen Air Force Base, where the Dec. 10 missile test was conducted.