WASHINGTON – The Navy and Coast Guard have finished their search off the South Carolina coast for pieces of wreckage from the Chinese spy balloon that was shot down two weeks ago, officials said Friday.

Navy and Coast Guard crews have been combing through the large debris field – about the size of 15 football fields – since President Joe Biden ordered the military to shoot the balloon down on Feb. 4.

The Pentagon said the airship flew at about 60,000 feet – safely above civilian air traffic – as it crossed the United States and was shot down as soon as it was over the Atlantic Ocean, where it was no longer considered a danger to people on the ground. As the balloon crossed the U.S., the Pentagon said it prevented it from gathering intelligence from the ground.

“Recovery operations concluded [Thursday] off the coast of South Carolina, after U.S. Navy assets … successfully located and retrieved debris from the high-altitude [Chinese] surveillance balloon,” Northern Command said in a statement issued Friday. “Final pieces of debris are being transferred to the Federal Bureau of Investigation laboratory in Virginia for counterintelligence exploitation.”

The Chinese balloon incident sparked a heightened scrutiny of U.S. airspace that has led to several other shoot-downs. A few days after the balloon was taken out, U.S. fighter jets shot down what officials said were different “high-altitude objects” on Feb. 10, Feb. 11 and Feb. 12. Few details have been revealed yet about those objects, including from where they emanated.

“We don't yet know exactly what these three objects were,” Biden said Thursday in a public address from the White House about the shoot-downs. “But nothing right now suggests they were related to China's spy balloon program, or they were surveillance vehicles from any other country.”

Those three objects were shot down mainly because at about 45,000 feet they posed a threat to civilian air traffic, Biden and the Pentagon have said. They have also noted the objects were much smaller than the Chinese balloon, which measured 200 feet in height and carried a payload about the size of three buses.

Air Force Brig. Gen. Pat Ryder, the top Pentagon spokesman, has said the crews in the debris field were searching for pieces of surveillance equipment from the balloon and other clues to explain what it was doing in U.S. airspace. Defense officials said the airship was able to propel itself and, being a spy balloon, it also could have been outfitted with explosives to self-destruct. It has not been revealed yet, however, whether crews found any explosives.

Since the Chinese balloon was first spotted near Alaska in late January, the Pentagon has said it was part of a Chinese fleet of spy balloons that have been floated over other countries on five continents. The balloons have also hovered over U.S. territory on at least four previous occasions in recent years – one other time during Biden’s term and three times during former President Donald Trump’s administration, defense officials have said.

Biden said he plans to speak soon with Chinese President Xi Jinping and demand answers about the balloon.

“We are going to get to the bottom of this,” he said. “But I make no apologies for taking down that balloon.”