The hours-long closure of El Paso airspace stemmed from the use of an anti-drone laser deployed by Customs and Border Protection, according to reports from The New York Times and the Associated Press. Sources tell The Times that CBP officials didn’t give the Federal Aviation Administration “enough time to assess the risks to commercial aircraft,” leading to the abrupt shutdown.

On Wednesday, the FAA closed the airspace around El Paso International Airport, citing “special security reasons.” The move impacted commercial flights and emergency medical transportation. Though the agency initially said the closure would last 10 days, it reopened the airspace just hours later. At the time, US Transportation Secretary Sean Duffy said in a post on X that the “FAA and DOW [Department of War] acted swiftly to address a cartel drone incursion,” adding that the “threat has been neutralized.”

The New York Times reports that CBP officials “thought they were firing on a cartel drone,” but it was actually a party balloon. Sources tell CBS News that one balloon was shot down. The Pentagon reportedly provided the CBP with the anti-laser technology. The CBP deployed the laser in response to the drones that Trump administration officials claim Mexican cartels are using to smuggle drugs and surveil border patrol agents, as noted by The New York Times. Mexican President Claudia Sheinbaum has pushed back on these claims.

Reuters reports that the anti-drone technology used was AeroVironment’s LOCUST, a 20-kilowatt direct-energy weapon designed to take down drones. The CBP worked with the Pentagon to deploy the laser near Fort Bliss, a US Army base in El Paso, “without coordinating with the FAA,” according to the Associated Press.

Lawmakers are pressing Trump administration officials for answers about the airspace closure, with Sen. Jack Reed (D-RI) saying federal agencies must provide a “full accounting of what occurred in US airspace, whether proper safety protocols were followed, and why public communications appear to have been inconsistent.” Texas Representative Veronica Escobar says the airspace closure was “the result of incompetence at the highest levels of the administration,” and that she’s working to get “all the answers we deserve.”