On Saturday, the U.S. Air Force shot down the suspected spy balloon over the Atlantic Ocean after it had floated southeastward across the United States. Defense Secretary Lloyd Austin said the mission to shoot down the balloon was conducted in coordination with the Canadian government.

The USS Carter Hall has started to collect debris near the splashdown site, as the USNS Pathfinder maps the ocean floor, using sonar, the Defense Department announced Monday during a briefing.

Air Force Gen. Glen VanHerck, commander of the North American Aerospace Defense Command and U.S. Northern Command, said ocean currents could make it impossible to collect all of the debris and warned the public against collecting any balloon fragments that wash ashore.

“I would remind you that due to ocean currents, it’s possible that there may be some debris that does float ashore,” VanHerck said during Monday’s briefing. “And so what we would ask of the public, and you can help me with this, is avoid contact. Contact local law enforcement immediately to take care of any of that debris.”

The Defense Department also announced that the Navy is working to produce a map showing the full debris field.

“We expect the debris field to be of the rough order of magnitude of about 1,500 meters by 1,500 meters, and so, you know, more than 15 football fields by 15 football fields,” VanHerck said, while adding that the Navy will also determine whether the scene is safe.

They’ll be using “unmanned underwater vehicles using side scan sonar to further locate sunken debris. And so we expect them to get on there and to do some additional categorization of potential threats such as explosives that may be on, hazardous materials that could be in batteries, et cetera, so we’re working very hard,” VanHerck added.

The destruction of the surveillance balloon, discovered floating over the United States last week, has complicated what were already considered strained relations between the United States and China, leading to U.S. Secretary of State Antony Blinken‘s planned visit to Beijing to be postponed.

“The discovery of this high-altitude surveillance balloon in the days that preceded the secretary’s visit, of course, undermined the point of that visit,” State Department Spokesperson Ned Price said during a briefing Monday. “We would not have been able to conduct the important business that Secretary Blinken was looking forward to doing on the ground in Beijing in that context.”

“We’ll determine when it’s appropriate to potentially look to travel to the PRC to have the type of discussion that we think it’s incumbent on our countries to have,” Price added, referring to China by the initials of its official name, the People’s Republic of China.

On Monday, China’s foreign ministry spokesperson Mao Ning urged both sides, “especially the United States” to “remain calm.”

“The entry of the strayed balloon into U.S. airspace was a purely unintended, unexpected and isolated incident,” Mao said. “It tests, however, whether the United States is sincere about stabilizing and improving its relations with China and whether it can properly manage a crisis.”

As the Navy works to recover as much of the balloon debris as possible, the Defense Department said Monday that it is still working out where it will be sent to be examined.

“I don’t know where the debris’ going to go for a final analysis, but I will tell you that certainly the intel community, along with the law enforcement community that works this under counterintelligence, will take a good look at it,” VanHerck said. “So we look forward to moving forward there.”