(AP) — The sudden and surprising airspace closure over El Paso, Texas, stemmed from the Pentagon’s plans to test a laser for use in shooting down drones used by Mexican drug cartels, according to three people familiar with the situation who were granted anonymity to share sensitive details.

That caused friction with the Federal Aviation Administration, which wanted to ensure commercial air safety and the two agencies sought to coordinate, according to two of the people. Despite a meeting scheduled later this month to discuss the issue, the Pentagon wanted to go ahead and test it, prompting the FAA to shutter the airspace. It was not clear whether the laser was ultimately deployed.

Transportation Secretary Sean Duffy said earlier that a response to an incursion by Mexican cartel drones had led to the airspace closure and that the threat had been neutralized. Drone incursions are not uncommon along the southern border.

Officials at the White House, FAA and Department of Transportation did not respond immediately to a request to comment on the dispute. The Pentagon said it had nothing to add to its statement that largely mirrored Duffy’s comment.