A high-ranking military official told senators Thursday that he was alarmed by the thousands of drones flying over the southern border and warned that the incursions represent a "growing" potential threat to the nation's defense.

"The number of incursions was something that was alarming to me as I took command last month," Air Force Gen. Gregory Guillot said in response to a question from Sen. Ted Budd at a Senate Armed Services Committee hearing. 

Guillot, the commander of North American Aerospace Defense Command and U.S. Northern Command, said the exact number of drones is hard to pinpoint, but from discussions with U.S. Customs and Border Protection and the Justice Department, he believes there are "probably" more than a thousand a month.

"I don't know the actual number - I don't think anybody does - but it's in the thousands," he told Budd, a Republican from North Carolina. 

Asked whether he sees the unmanned aircraft as a security threat, Guillot said he hasn't "seen any of them manifest in a threat to the level of national defense."

"But I see the potential only growing," Guillot added.

Cartel members from Mexico use the drones to monitor the movement of agents on patrol near the Mexican border, U.S. Customs and Border Protection said in a statement last year. 

In a January 2023 bust at a stash house that smugglers were using to transport migrants over the border illegally, Customs and Border officials discovered video footage showing federal agents being recorded by drones. 

"Human smugglers using drones to surveil the Border Patrol is a growing trend that we've observed along the border," San Diego Sector Chief Patrol Agent Aaron M. Heitke said in a statement. "This technology provides transnational criminal organizations with new capability that they are eager to exploit."