Passengers who came down with a mystery illness on a Delta Airlines flight were found to have elevated levels of carbon monoxide in their bodies.
ABC News reported that several passengers became ill on the Delta flight from Atlanta to Denver on Sunday.
They were found to have elevated levels of carbon monoxide in their bodies, Tulsa Fire Department Stan May said.
Once passengers went outside and breathed fresh air, their levels returned to normal, he said.
"The flight crew of Delta flight 1817 from Atlanta to Denver elected to divert to Tulsa when a few customers reported feeling ill," Delta said in a statement. "The safety and security of our customers is our top priority."