After reviewing thousands of tips, federal law enforcement officials on Saturday reaffirmed that mysterious drones spotted in the Northeast in recent weeks pose no national security threat and in most cases are not even drones.

Investigators reviewing video footage and interviews with witnesses have so far determined that at least some of the roaming objects were manned aircraft, such as airplanes or helicopters, that were misidentified as drones, according to officials from the F.B.I., Department of Homeland Security and Federal Aviation Administration, who briefed reporters on the condition of anonymity on Saturday because they were not authorized to speak publicly.

Federal officials have received nearly 5,000 tips on drone sightings in recent weeks and deemed only 100 of them worthy of further investigation, an F.BI. official said.

The U.S. officials said they had confirmed drone sightings over military bases in New Jersey, including Picatinny Arsenal, but they had no evidence the devices were operated by a foreign government or authority. U.S. national security officials have not been able to identify the operators of the drones.

The rise of the drone sightings have caused alarm in communities in the Northeast as residents have increasingly looked to the sky with a cellphone in hand, hoping to learn more about the floating devices. State and local leaders have accused the Biden administration of not taking the drone sightings seriously. The airborne devices have captured the attention of Americans 22 months after a giant Chinese spy balloon drifted over the United States, causing a diplomatic crisis. President Biden eventually ordered it shot down.