DENVER (AP) — Doughnuts were delivered Wednesday by drone to Denver’s mayor and the city’s police and fire departments in an event that provided a glimpse into what companies hope will be a quick, inexpensive way to get merchandise to customers.

Denver’s LaMar’s Donuts hired Austin, Texas-based company Drone Dispatch to deliver four boxes of doughnuts using piloted drones flown from parking lots within a block of the delivery targets.

LaMar’s spokesman Tami Osifodunrin said Federal Aviation Administration regulations prohibit commercial drone pilots from losing sight of drones.

Denver Mayor Michael Hancock was outside city hall when a drone delivered doughnuts.

“This is exciting stuff and I think as we get ready for not only drones in the air, and get ready for autonomous vehicles, this is our future this is how we’re going to become a more efficient 21st century nation, society quite frankly,” Hancock said.

FAA officials said they were investigating to ensure the deliveries followed federal rules governing commercial drone use in populated areas. The FAA has rules that govern drone altitude, proximity to airports, and flying over people who are not part of the crew flying the drone. The organizers said they took care to comply with regulations.

“We’re doing it completely legal, we have very, very short deliveries from the drone where we have a safe takeoff location and the landing area is a Drone Dispatch team member who’s receiving the box of doughnuts,” said Chris Bonnet, CEO of Drone Dispatch.

The drones took off from parking lots near the Denver City and County Building, the police department, the fire department and an alleyway near a pedestrian mall.

Amazon and other companies have been testing autonomous drones for deliveries, while drone maker Flirtey last year began limited deliveries for 7-Eleven in Reno, Nevada.

The doughnuts were delivered as part of a week of celebrating a tradition that dates to World War I, where Salvation Army volunteers made doughnuts for soldiers on the front lines. National Doughnut Day is celebrated the first Friday of every June.