A United States senator has called for mysterious drones spotted flying over sensitive areas of New Jersey and other parts of the mid-Atlantic region to be "shot down, if necessary".

It comes as residents in the US state reported more than 40 drones over the region, sparking the White House, the FBI and the Pentagon to investigate.

"We should be doing some very urgent intelligence analysis and take them out of the skies, especially if they're flying over airports or military bases," Senator Richard Blumenthal of Connecticut said, as concerns about the drones spread across Capitol Hill.

People in the region are also concerned that the drones may be sharing airspace with commercial airlines, the senator said, demanding more transparency from the Biden administration.

However according to the White House, FBI and Homeland Security there is no evidence that drone sightings reported in New Jersey posed national security or safety threats.

On Thursday, local time, the White House said that a review of the reported sightings shows that many of them are actually manned aircraft being flown lawfully.

The White House National Security spokesman John Kirby said there were no reported sightings in any restricted airspace.

"We have no evidence at this time that the reported drone sightings pose a national security or a public safety threat, or have a foreign nexus," Mr Kirby said, echoing statements from the Pentagon.

Pentagon spokesperson Sabrina Singh said they are not US military drones.

In a joint statement issued on Thursday, the FBI and the Department of Homeland Security said they and their federal partners, in close coordination with the New Jersey State Police, "continue to deploy personnel and technology to investigate this situation and confirm whether the reported drone flights are actually drones or are instead manned aircraft or otherwise inaccurate sightings".

The agencies said they have not corroborated any of the reported sightings with electronic detection, and that reviews of available images appear to show many of the reported drones are actually manned aircraft.

"There are no reported or confirmed drone sightings in any restricted air space," according to the statement.

Tony Perry, mayor of Middletown, New Jersey, told CNN on Thursday that in the past week or so there have been more than 40 drones spotted over his town at night.

He said the drones are "SUV-sized" and fly at upward of 96 to 110 kilometres per hour.

"I'm not sure how anyone can just sit there and say that there's no imminent threat," he said.

"I don't think the federal government has taken it seriously to date," Cr Perry added.

In a post on the social media platform X, New Jersey Legislature Assemblywoman Dawn Fantasia described the drones as up to 1.8 metres in diameter and sometimes travelling with their lights switched off.

Drones are legal in New Jersey for recreational and commercial use but are subject to local and Federal Aviation Administration (FAA) regulations and flight restrictions.

Operators must be FAA certified.

Most, but not all, of the drones spotted in New Jersey appeared to be larger than those typically used by hobbyists.

John Duesler, president of the Pennsylvania Drone Association, said witnesses may be confused about what they are seeing, and noted it's hard to know the size of the drones or how close they might be.

"There are certainly big drones, such as agricultural drones, but typically they are not the type you see flying around in urban or suburban spaces," Mr Duesler.

He said the public wants to know what's going on, as did Senator Cory Booker of New Jersey.

AP/Reuters