The camera-equipped drones will allow police to scan nearby crowds with long-distance and infrared zoom, and are intended to help thwart low-tech terror attacks like the one in London last month.

“It’s really something new we’re going to be using where we have a very dense population of people between the village and the start line. They will not be over spectator areas, and they will be providing live video feeds into public safety command centers,” an official said at a Wednesday security briefing, according to the Boston Herald.

While drones can fly without any tethers, the marathon drones are attached to thin wires as a means of keeping them powered up in the sky for days at a time.

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The runners, meanwhile, can look forward to a relatively drone-free race once they leave the starting line as security officials do not plan to deploy them anywhere else. As for spectators, a guide to the race encourages them to not fly them.

“Public safety officials are asking the public to assist in creating a No-Drone Zone along the entire course at this year’s Boston Marathon. The use of drones (unmanned aerial vehicles) anywhere in the area of the course, including above runners and spectators, is strongly discouraged,” according to the official event guide.

The introduction of security drones at the marathon comes at a time of public debate over when and how U.S. law enforcement agencies should be able to use the devices. In Connecticut, for instance, law makers are debating a measure that would let police use drones with deadly weapons in some circumstances. (Meanwhile, in France, the military are training eagles to take down hostile drowns.)

The Boston Marathon will take place as always on the state holiday of Patriots Day, which falls on April 17 this year. The race will mark the four-year anniversary of the deadly Boston Marathon bombings in 2013.