A Delta Air Lines plane at Chicago's Midway International Airport was grounded and quarantined Thursday afternoon.
According to NBC Chicago the flight landed just after 3:30 p.m. but passengers were unable to leave the plane.
Department of Aviation spokeswoman Karen Pride said crews were called to treat a passenger with an unspecified medical issue.
The Detroit Free Press is reporting that the plane was traveling from Detroit, and spent two hours in quarantine before passangers were allowed to leave.
The Center for Disease Control also confirmed that they were investigating reports of a "possible illness."
Midway remains open.