The Federal Aviation Administration has issued a monthlong ban on drone flights over a large swath of New Jersey, the first broad prohibition of its kind since the authorities began investigating a spate of sightings last month that set off fear and speculation.

The ban began late on Wednesday and will continue through Jan. 17, according to an F.A.A. alert.

The notification cited “special security reasons” for prohibiting flights in airspace near 22 New Jersey communities, including three of the state’s largest cities, Camden, Elizabeth and Jersey City.

Only drone pilots authorized to operate for national defense, law enforcement or disaster response purposes are permitted to send the unmanned crafts aloft. Operators of drones used for commercial purposes may apply for a waiver after providing a “valid statement of work,” the F.A.A. alert said.

Federal aviation officials could not be immediately reached for comment on the decision.

The F.B.I. began investigating reports of drone sightings in New Jersey a month ago. Soon after, the authorities banned drones from operating near the Bedminster golf course run by President-elect Donald J. Trump and the Picatinny Arsenal, a large U.S. Army center.

Widespread news coverage followed. So, too, did thousands of additional reports of sightings over New Jersey, New York and several other states in the Northeast. Federal officials have issued repeated assurances that there is no security threat, and have said that most sightings appear to be of either airplanes or helicopters.

That has done little to assuage the public and some elected officials, including those who have speculated that the electronic devices are being used for nefarious reasons.

This is a developing story. Check back for updates.