An FBI official told reporters during an impromptu briefing that the agency was working with 50 local, state and federal partners to look into increased reports. The official said less than 100 of the over 5,000 reported sightings had turned out to merit further investigation, and all of the large fixed-wing reported sightings so far involved manned aircraft.

"The combination of efforts so far ... to include technical equipment, tip line information and noted consults has ... not found any evidence to support large-scale (unmanned aerial systems) activities," the official said, adding that many of the sightings occurred along regular flight paths.

Extensive efforts were underway to investigate the remaining cases, using interviews and analyses of radar and intelligence, the official added.

"We can't ignore the sightings that have been there," the official said. "We're doing our best to find the origin of those drone activities, but I think there has been a slight over-reaction."

A spate of reported drone sightings that began in New Jersey in mid-November spread in recent days to include Maryland, Massachusetts and other states. The sightings have garnered media attention and prompted creation of a Facebook page called "New Jersey Mystery Drones - let's solve it" with 56,000 online members.

U.S. President Joe Biden is receiving regular updates on the issue, a White House official said.

On Cape Cod in Massachusetts, residents and a police officer in Harwich reported seeing 10-15 drones flying in the Friday night sky, the Boston Herald reported.

Police relayed the information to the Boston FBI and Massachusetts State Police.

Gov. Maura Healey said on Facebook that she is also “aware of a growing number of drone sightings across Massachusetts and we’re monitoring the situation closely.”

New York Governor Kathy Hochul on Saturday called for a boost in federal law enforcement efforts after the runways at a local airport in the Hudson Valley were shut down for one hour due to drone activity on Friday.

"This has gone too far," Hochul said in a statement on the social media network X, urging the Biden administration to boost law enforcement in New York and other areas, and calling on Congress to pass drone reform legislation.

An official with the Federal Aviation Administration said a temporary ban on drone activity had been put in place over Picatinny Arsenal, a military base in Wharton, New Jersey, that was due to expire on Dec. 26 and could be made permanent.

There had been drone sightings over Picatinny and another naval weapons station in December, a military official told reporters, but there was no intelligence or observation that they were linked to a foreign actor or had malicious intent. Drone operations over military installations are generally banned, but occur from time to time, the official added.

A second ban was put in place over Trump National Golf Club in Bedminster, New Jersey, that was due to expire on Dec. 20, but could be extended, the FAA official said.