By Rene Marsh and Amir Vera, CNN

(CNN) -- Federal authorities are investigating after an air traffic controller on an overnight shift at McCarran International Airport in Las Vegas repeatedly gave incoherent directions and responses to pilots.

The conversations were captured on air traffic control audio on Wednesday and confirmed by the Federal Aviation Administration.

In the recording, the controller can be heard slurring her words and giving unclear instructions as pilots repeatedly ask her to repeat herself.

"Sorry I'm choking a little bit," the controller says at one point during the 30-minute recording.

At another point, a concerned pilot says, "I hate to ask this but ... do you have a supervisor?"

The air traffic controller eventually becomes unresponsive, according to the recording. Later, she could be heard coughing before someone apparently enters the room and asks if she is OK. Another controller took over a short while later, according to the audio recording.

The controller was responsible for guiding the movements of 29 pilots that day, according to CNN affiliate KSNV.

"The FAA is deeply concerned by the incident, is thoroughly investigating what occurred," FAA spokesman Gregory Martin said in a statement. The FAA described the controller as "incapacitated" during the incident.

She is currently restricted from working air traffic, and the matter is under investigation, the agency said.

She was the sole air traffic controller in the tower at the time. KSNV reported that another controller was on duty but taking a break.

The FAA said no "safety events" occurred during the incident and that it has made changes to its overnight shift staffing policies as a result.

The new policy requires two controllers in the air traffic control tower at all times for the first 90 minutes of the midnight shift and depending on the volume of traffic, according to KSNV.

The agency would not share more details about the controller and what caused her to become incoherent, citing privacy concerns.

The National Air Traffic Controllers Association, the labor union that represents FAA air traffic controllers, said in a statement it would cooperate with the FAA in the investigation.