A US-made drone believed to be used for reconnaissance was recovered in Philippine waters on Monday, police and naval officials have said.

The 3.65 meter (12-foot) unmanned drone was found by fishermen in waters off Masbate island, central Philippines, who alerted police, thinking they had pulled a bomb out of the water, AFP reports.

“A technical evaluation determined that the object is one unmanned aerial vehicle,” said provincial police chief, Senior Superintendent Heriberto Olitoquit.

The drone had been turned over to the Philippine Navy which will now take over the investigation.

“It appears to have been floating for quite some time,” Captain Rommel Galang, deputy commander of naval forces in the area, told AFP. “We will first study this drone but initially it appears to be a UAV used largely in reconnaissance.”

A statement released Monday from the US embassy in Manila said they were looking into the drone’s recovery.

“The recovered vehicle appears to be of the sort that is used as an air defense target in training exercises. This type of vehicle is not armed and not used for surveillance. We are trying to confirm this interpretation and to determine how and when it may have landed in the sea,” the statement said.

President Benigno Aquino confirmed in an interview with AFP last year that US drones were allowed to fly across the Philippines for surveillance purposes but were not allowed to conduct strikes. The Philippines has long been a close American ally, relying on the military superpower for weapons, and sought help against security threats such as Islamic militants in the country.