Was it drugs or alcohol? A medical emergency? Federal officials aren’t saying, but an air traffic controller at the Las Vegas tower had to be removed from her position last week after she began slurring her words and giving incoherent commands to pilots – then stopped talking altogether.

News sources say the timeline for the incident at McCarran International Airport was as follows:

The controller began to have trouble communicating in a clear and concise manner shortly after 11 pm, and was completely unresponsive by 11:47 pm. Paramedics were sent to the tower and a replacement took over her position at 11:54 pm.

Although the emergency was short-lived, it affected operations and caused concern among the pilots seeking instructions, who began radioing each other when they were unable to establish clear communications with the controller.

She was initially placed on leave but is now no longer working for the Federal Aviation Administration (FAA). The agency has declined to say whether she resigned or was terminated.

The FAA says it is “deeply concerned” by the incident, and will investigate what occurred and take immediate steps to modify its overnight shift staffing policies.