The Federal Aviation Administration, or FAA, is investigating the use of at least half a dozen drones that have violated airspace restrictions near stadiums this fall, The Washington Post reported Sunday. The news comes days after the FAA updated a 2009 notice criminalizing the flying of drones near or over sports stadiums during events.

Sightings of small drones have been reported at major football games since August, the Post reported. Small drones are mostly used by untrained sports fans who intend to record games and post the videos on the Internet. These remote-controlled aircraft are cheaply available and easy to fly, The Post reported, but FAA officials and aviation safety experts believe that the blades of the drones can be lethal, and the use of drones by amateurs poses a serious threat to the safety of people in crowded stadiums.

“It’s an absolute safety concern,” Marc Lovicott, a campus police spokesman at the University of Wisconsin-Madison, told The Post. “You never know what might be carried along with something like that.”

According to The Post, a 19-year-old was killed last year in Brooklyn after the amateur lost control of his drone helicopter and its blades cut off the top of his head. Authorities are also concerned about the use of drones near airports, according to The Post, which cited several cases reported by the FAA of people flying drones close to passenger aircraft.

Last month, the FAA updated a 2009 public notice prohibiting the use of “unmanned aircraft and remote controlled aircraft” near stadiums, adding that a violation could lead to a fine or imprisonment for up to a year.

The notice is "another attempt by the FAA to impose legal restriction on drones or model aircraft that never existed before,” Brendan Schulman, a New York-based attorney who represents several drone operators, said at the time.

The public notice bans airplane flights over open-air stadiums with 30,000 or more spectators. The FAA has also instructed pilots to avoid flying aircraft below 3,000 feet and within three miles of a Major League Baseball, National Football League or NCAA Division I college football game. The restrictions are active for an hour before and after an event.