A Delta flight made an emergency landing Saturday after passengers on board became ill.
The flight was traveling from Atlanta to Denver, but diverted to Tulsa, Oklahoma without warning.
Confused and panicked passengers deboarded, and were quarantined for several hours without explanation.
Medics treated 12 sick travelers who showed symptoms of carbon monoxide poisoning.
Passengers were transferred onto a different flight to Denver Saturday night.
Authorities confirmed Sunday the cause was carbon monoxide, but the source is still unknown.