This photograph was taken by a traveler at the Nashville airport.
CNN  — 

A Delta-operated SkyWest plane briefly emitted flames on the tarmac of Nashville International Airport on Friday morning. The plane was heading to Cincinnati, scheduled to depart at 6:34 a.m. CDT.

The plane had just turned on its engine and had not yet reached the runway when the flame started, according to airport spokeswoman Shannon Sumrall.

“The auxiliary power unit caught fire, but when they turned the engine back off the fire extinguished itself and the plane was brought back to the gate and all passengers were deboarded,” said Sumrall.

Delta described the incident as a flame instead of a sustained fire.

The plane “experienced a brief flame upon engine startup, which immediately dissipated. There was no fire and no emergency was declared. Technicians are evaluating the CRJ-200 aircraft and customers have been reaccommodated on alternate flights,” said spokesman Michael Thomas.

Thomas told CNN the flame resulted from “small excess fuel in the tailpipe of the engine being expunged from the rear of the engine.”

He said there were no injuries. The flight carried 50 passengers and three crew members.

CNN’s Sheena Jones, Carma Hassan, and Mary Helen Moore contributed to this report.