According to CNN, the USNS Bowditch attempted to recover two undersea drones about 100 miles off a port at Subic Bay near the Philippines when a Chinese ship placed a small boat into the water that picked up one of the U.S. vehicles.
Chinese naval personnel on the ship did not respond to initial contact from the U.S. after the Bowditch crew said the drone was American property, CNN reported.
ABC News says the U.S. deployed the unclassified drone into the South China Sea for ocean research.
The U.S. State Department has filed a formal diplomatic protest with China over the incident.