The grounding of aircraft at El Paso International Airport early Wednesday morning was in response to the U.S. military testing technology that can be used to take down drones, according to four sources familiar with the matter.

The testing was taking place in the proximity of the airport, raising concerns within the Federal Aviation Administration, which responded by issuing a Temporary Flight Restriction Notice, the sources said.

Three of the sources said the military testing, which was taking place near Fort Bliss, was of high-energy lasers that are designed to protect against drones from drug cartels that could cross over the U.S. border.

TheFederal Aviation Administration halted all flightsout of the El Paso International Airport inTexasfor 10 days for what it said were “special security reasons” before abruptly lifting the order.

It did not explain the about-face. A Trump administration official earlier told NBC News that Mexican cartel drones had breached American airspace and the Defense Department had disabled them.

There is no confirmation from the Pentagon that any drones were shot down, despite the statement from the administration official.

The military did recently shoot down a small party balloon, two of the sources said.

Two of the sources say a miscommunication, or possibly a dispute, between the FAA and Defense Department about whether the testing could impact commercial aviation that preceded the grounding of aircraft at El Paso airport.

They said the FAA issued the temporary restriction until the agency could get more information about the testing or be assured it wasn’t impacting aviation.

Some lawmakers on Capitol Hill told defense department officials that the grounding of flights was due to a counter-drone exercise that was not coordinated with the FAA, according to a fourth source familiar with the matter.

Source: Drudge Report