The Chinese military has returned a seized underwater probe to the US Navy in the South China Sea on Monday, the Pentagon has confirmed.
According to a BBC report, the drone was handed over close to the location it was seized, some 92km north-west of Subic Bay.
The Pentagon says the marine probe is a commercial craft that gathers unclassified data that can be used to help submarines navigate and determine sonar ranges in murky waters.
The defence official said it was not the first time the US Navy had lost such a probe. One was taken near Vietnam earlier this year, but who took it and what became of it remain unclear.
Last week's seizure was the first time China had "brazenly stolen a piece of US government property," the official said.
China said the drone had been snatched since it might pose a safety hazard to other vessels. It also said it "strongly opposed" US reconnaissance activities and had asked Washington to stop them.
The incident unfolded when a Chinese Dalang-III class submarine rescue ship stopped within 457.2 meters of the civilian-crewed USNS Bowditch and snatched one of a pair of probes. The Americans safely hoisted the other one back onto their ship.
The US official said the Chinese ship had been shadowing the Bowditch for "a number of days." China's seizure of the bright-yellow, unmanned underwater vehicle has prompted sharp words between Washington and Beijing, with US diplomats protesting the "unlawful" incident.
President-elect Donald Trump further ratcheted up tensions by accusing China of theft. "China steals United States Navy research drone in international waters -- rips it out of water and takes it to China in unpresidented act," he wrote in a misspelled tweet he later corrected.
(With inputs from PTI)