With drones prohibited from the Boston Marathon, police say a new piece of technology is helping them enforce the policy.
According to Massachusetts State Police, a system similar to "ShotSpotter," which detects gunfire, is being used to keep the marathon route safe.
The system alerts police to the sound and location of a drone.
So far, police say security has been smooth.
"We feel good about the security plan," said Massachusetts State Police Col. Tim Alben in a text message to NBC News. "No problems to report."