The US drone with model number BQM 74-E was launched from US warship USS Chafee during a military exercise "Valiant Shield" Sep 19, 2012, Xinhua quoted Tina Malone, spokesperson for the US embassy in Manila, as saying.
"It appears that ocean currents brought the drone to where it washed ashore last week off Masbate island," Malone said.
Philippines Armed Forces spokesman Col. Arnulfo Marcelo Burgos said in a separate statement that the aerial vehicle was never used in the country.
"This was never used within the Philippine territory during our military exercise with the US. This was probably used somewhere in the Pacific during an exercise," Burgos said.
He said the UAV was not a spy drone.
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"The drone found in Masbate is not a spy plane but an aerial target drone. Its orange colour and US Navy logo suggests that it is used primarily to simulate enemy missiles and aircraft during exercises," he was quoted as saying.
A diver found the drone Sunday and initially mistook the item to be a bomb.
Guam is around 2,500 km from the Philippines. A US military installation on Guam, Andersen Air Force Base, was used by B-52 bombers during the decade-long Vietnam War in the 1970s.