Officials and experts say some witnesses may actually be seeing planes or helicopters rather than drones, or perhaps are confused about the size of the devices they’re seeing.

“There are certainly big drones, such as a agricultural drones, but typically they are not the type you see flying around in urban or suburban spaces,” John Duesler, president of the Pennsylvania Drone Association, said Thursday. The organization with about 350 members, is headquartered in Pittston, Pennsylvania.

“I wonder a little bit if it’s sort of a type of fish story, as in ‘I caught a fish this big!’ type of a thing,” Deusler added. “At night, it’s hard to see how big the drones are, especially because they can be either closer or further away from you. To get that perspective of how big they are is really difficult.”

Who sent the drones?

Authorities say they do not know who is behind the drones.

The FBI, Homeland Security and state police are investigating the sightings. Authorities say they don’t know if it is one drone that has been spotted many times or if there are multiple aircraft being flown in a coordinated effort.

Speculation has raged online, with some expressing concerns that the drone or drones could be part of a nefarious plot by foreign agents. Officials stress that ongoing state and federal investigations have found no evidence to support those fears.

Two Republican Jersey Shore-area congressmen, Smith and U.S. Rep. Jeff Van Drew, have called on the military to shoot down the drones, citing safety concerns.

The Pentagon insists the drones do not represent a threat from abroad.

Pentagon spokesperson Maj. Gen. Pat Ryder said Thursday that the military’s initial assessment after consulting with the Department of Homeland Security and the National Security Council — that the drones are not of foreign origin — remains unchanged.

Pentagon spokeswoman Sabrina Singh said Wednesday that the aircraft are not U.S. military drones.

Are drones allowed in New Jersey?

The flying of drones for recreational and commercial use is legal in New Jersey, but it is subject to local and Federal Aviation Administration regulations and flight restrictions.

Operators must be FAA certified.

Have drones been spotted anywhere else?

Sightings also have been reported in neighboring New York and Pennsylvania.

Drones were also spotted last month in the U.K. The U.S. Air Force said several small unmanned aircraft were detected near four military bases in England that are used by American forces.

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Associated Press reporters Tara Copp in Washington, D.C., and Mark Scolforo in Harrisburg, Pennsylvania, contributed.