DENVER (KDVR) — A Frontier Airlines flight had to return to Denver on Tuesday night because of an issue on the plane.

The flight was to Raleigh, North Carolina, according to a Denver International Airport spokesperson. The spokesperson first told FOX31 it was a medical situation. They later said it was a mechanical situation.

FOX31 confirmed through FlightAware that Frontier flight 560 returned to the Denver airport shortly after departure on Tuesday evening.

The pilot can be heard reporting an odor in the cockpit, according to air traffic control recordings on The pilot said the odor was not smoke but something “indicating that we have some kind of contamination in the cabin.”

Frontier Airlines released this account of what happened:

Earlier this evening, shortly following takeoff from Denver International Airport, Flight 560 bound for Raleigh-Durham with 160 passengers on board, experienced a fume event which prompted the flight crew to return the aircraft to Denver and request support from emergency medical personnel as a matter of precaution. A number of passengers and the flight crew were seen by EMS professionals at the gate. No reports of individuals requiring further medical treatment have been received. A replacement aircraft is scheduled to operate the flight with a departure later this evening.

Frontier Airlines

FlightAware shows the plane took off at 6:32 p.m. and arrived back in Denver at 7:10 p.m.