Mystery continues to swirl after nearly a month of drone sightings over New Jersey and other US states, alarming some residents.

US authorities have been unable to provide definitive answers, saying only that the objects are not believed to pose a danger to the public or national security.

On Sunday, Homeland Security Secretary Alejandro Mayorkas confirmed the sightings included drones, as well as manned aircraft commonly mistaken for drones.

He added that he knows of “no foreign involvement” to do with the unmanned aerial vehicles.

Some lawmakers have criticised the government’s handling of the drone reports and the lack of public information.

The drone sightings have prompted a wide-range of baseless conspiracy theories, including that they are searching for nuclear weapons, radioactive “dirty bombs” or are form part of an impending invasion by aliens.