The U.S. is tracking a high-altitude balloon flying over the Western part of the country, U.S. officials told CBS News. Military aircraft have spotted the balloon and determined it is not a threat, but its origin and purpose is still unknown, the officials said.

Sources familiar with the matter who spoke on the condition of anonymity said the balloon was drifting east in the jetstream on Friday. Earlier in the day, one official said the balloon was over Colorado. Its presence prompted enough concern that the military sent aircraft to investigate.

The developments come one year after tensions between the U.S. and China ratcheted to new heights after a Chinese balloon carrying sophisticated spying equipment flew over the continental U.S. for several days. 

The Chinese foreign ministry claimed that the balloon was meant to collect weather data and had “deviated far from its planned course” due to high winds. The U.S. military ultimately shot it down off the coast of South Carolina on Feb. 4, 2023, and recovered the wreckage.

The spy balloon became a political headache for President Biden, who faced criticism from Republicans over his decision to allow it to transit over the U.S. for nearly a week before ordering it shot down. Biden officials said they waited until it was off the coast to minimize the risk to civilians on the ground. But lawmakers questioned why it couldn’t have been brought down when it was near Alaska’s coast, before crossing the U.S.

Though the Pentagon eventually concluded the balloon did not transmit information back to China, its presence put the U.S. military on high alert for other objects in U.S. airspace. Fighter jets shot down several unidentified objects over the U.S. and Canada over the following weeks.

The military couldn’t find any debris from those objects, and the search was called off due to dangerous weather conditions. Mr. Biden said the unidentified objects were not believed to be connected to China’s spy balloon program.

“The intelligence community’s current assessment is that these three objects were mostly balloons tied to private companies, recreation or research institutions studying weather or conducting other scientific research,” the president said. 

The Chinese spy balloon became a major diplomatic point of contention between the U.S. and China, prompting Secretary of State Antony Blinken to cancel a trip to Beijing in February 2023. Blinken eventually made the trip in June to try to soothe rising tensions over a number of issues, including the balloon and the Chinese military’s assertiveness in the South China Sea.