U.S. national security agencies are examining hundreds of new UFO reports, a senior national intelligence official told Politico.

A total of 510 unidentified aerial phenomena observed in protected airspace or near important facilities had been reported as of last August, according to the director of national intelligence's report to Congress.

Of those, 366 have been since the preliminary assessment was published in 2021 - an increase attributed to "reduced stigma" about the reports and a better understanding of the intelligence and security threats these phenomena may pose.

According to the report, more than half of these new sightings, most of which were reported by Navy and Air Force pilots, show unremarkable characteristics. 26 were characterized as drones; 163 were labeled as balloons; and six were described as clutter.

Nevertheless, there remain 171 cases in which the objects demonstrated unusual flight characteristics or capabilities, the report said. Few details were provided about these unidentified objects, although the report notes that no U.S. aircraft have ever encountered a UFO, and sightings so far have not caused adverse health effects.

The 12-page report, which does not specify when each sighting occurred, is an unclassified account of the classified version that has been delivered to Congress.

In recent weeks, other senior officials have said they have yet to find any evidence that the unidentified vehicles are of alien origin or indicate the existence of a nonhuman being.