Emergency and fire crews responded to a major North Carolina airport after about a dozen passengers and crew members on a flight from the U.S. Virgin Islands complained of sickness.

WCNC-TV reported that seven US Airways crew members were taken from Charlotte-Douglas International Airport Saturday night after they complained of headaches and nausea.

The crew members had been onboard a plane that had just arrived from St. Thomas in the U.S. Virgin Islands. Five passengers from that flight were treated on the scene.

Shortly after the plane took off from St. Thomas, crew members noticed a slight odor on board and alerted authorities in Charlotte.

Investigators are working to determine what caused the odor, and the plane has been taken out of service.