Amid growing reports of drone-related incidents, U.S. government agencies are working with state and local police in developing technology to defend against drone incursions. Federal forces include the Department of Homeland Security, the Department of Defense and the Federal Aviation Administration.

The Department of Homeland Security says it “works side-by-side with our interagency partners.” Other agencies declined to comment.

Reuters reports there is at least one known field test, in New York City last New Year’s Eve, when New York police used a microwave-based system to track a commercially available drone at Times Square and send it back to its operator. Results were mixed due to interference from broadcast media covering the event.

Being able to neutralize a drone and identify its operator is essential to enforcement efforts. “You need enough power to override the transmitter. If I just jam it so it can’t receive signals, it’s probably going to crash. But if I know the transmission codes the drone is using, I can control that object,” says retired U.S. Marines Lt. Col. Muddy Watters, an electronic warfare expert.

But U.S. authorities are limited in their efforts. For instance, in 2012 Congress barred the FAA from regulating recreational drones. A Reuters analysis of FAA data indicates only one in 10 operators were identified after unauthorized drone sightings in 2014, and only 2 percent of those cases resulted in enforcement actions.

More than 1 million drones of all kinds are expected to be sold in the United States this year, compared to 430,000 in 2014 and 120,000 in 2013, according to the Consumer Electronics Association. U.S. pilots have reported more than 650 drone sightings this year, as of Aug. 9, more than double the 238 for all of 2014, the FAA says.