TOKYO (AP) – Japan’s state and navy police raided a Japanese naval academy Saturday over an alleged leak of sensitive warship technology data shared between Japan and America, officials said.

The case involves American-developed technology of high-tech Aegis radar on several advanced Japanese destroyers that is also used by American warships carrying missile interceptors. It has alarmed officials as the allies accelerate their joint missile defense development amid North Korean missile and nuclear threat.

Defense officials acknowledged the raid Saturday, but refused to provide details.

“We cannot make a comment regarding investigation,” said Navy spokesman Yutaka Fujisawa.

Investigators from Kanagawa state and Maritime Self-Defense Forces believe that computer disks containing the sensitive data were illegally copied and circulated among dozens of students and instructors at the First Service School in Etajima in western Japan, public broadcaster NHK reported Saturday.

The case surfaced in March when police found one of the disks at the home of a Japanese naval officer in Kanagawa during a separate investigation of his Chinese wife over her immigration status.

The 33-year petty officer second class was not authorized to possess the data. Police have been investigating how the disk ended up at his home and how its contents were circulated among naval students and other officers, Kyodo News agency said.

The raid over the alleged violation of the 1954 law concerning protection of secrets under bilateral security pact is reportedly the first at a Japanese naval academy.

Secretary of Defense Gates expressed strong concern about the data leak during talks in Washington with Japanese Defense Minister Fumio Kyuma in late April.

Japan began deploying its first advanced Patriot missile defense system in March, and also plans to introduce Standard Missile-3 interceptors on its destroyers over the next few years.