– The Pentagon says China has returned the unmanned underwater drone the Chinese Navy seized last week.

In a statement issued late Monday, Pentagon press secretary Peter Cook says the Chinese Navy vessel that had seized the drone Thursday returned it near the location where it had been taken. The incident occurred in the South China Sea near the Philippines.

Cook says the U.S. will continue to investigate the incident. Earlier Monday he had said U.S. and Chinese officials, including military leaders, were working out logistical details for the return.

The U.S. says the drone was being operated by civilian contractors collecting unclassified scientific data in international waters. Officials say a noncombat ship was recovering two drones when a Chinese ship approached, launched a small boat and picked up one of them.

The controversy picked up momentum Saturday evening after President-elect Donald Trump, after holding a rally to thank supporters for his election, posted on Twitter that the Chinese government should be told "we don't want the drone they stole back" and "let them keep it!"

This comes after United States officials had confirmed that they "secured an understanding" for the return of the device. Trump's tweet Saturday evening may extend one of the most serious incidents between the American and the Chinese militaries in years.

The U.S. lodged a formal diplomatic complaint and demanded the drone back. A Pentagon spokesman said the drone costs about $150,000 and is largely commercial, off-the-shelf technology.