MANILA, Philippines (AP) — U.S. officials say an unarmed drone found off the Philippines was launched from a U.S. Navy ship during a combat exercise off Guam last year and may have been washed by ocean currents toward central Masbate province.

U.S. Embassy spokeswoman Bettina Malone said Tuesday that the BQM-74E drone was launched from the USS Chafee in September.

The Philippine navy deployed a ship with ordnance experts after a diver and fishermen who found the drone over the weekend reported it may have been a bomb. The discovery sparked concerns because U.S. troops are allowed to engage in exercises with local troops but are legally barred from engaging in combat operations in the country.

Philippine diplomats have been assured by U.S. officials the drone was neither armed nor used for surveillance.