The FBI and FAA are investigating the transfer of a troubled passenger from a United flight in Chicago

(CNN) – The FBI and Federal Aviation Administration (FAA) are investigating an incident involving an “unruly passenger” on a commercial flight that took two passengers and one flight attendant to the hospital.

United Airlines says a “nuisance customer” on Flight 476 from San Francisco “was removed by law enforcement” after the flight landed in Chicago early Sunday morning.

“A member of the flight attendant’s crew has been taken to hospital for evaluation,” United said in a statement to CNN. “We are grateful to our crew for handling this challenging situation professionally and for prioritizing the safety of our team and our customers.”

“United Airlines Flight 476, a Boeing 777-200, landed safely at Chicago O’Hare International Airport around 6 a.m. Sunday after the crew reported an unruly passenger,” the Federal Aviation Administration said in a statement.

Chicago police said a total of three people on the plane were taken to Resurrection Hospital for “observation,” adding that no criminal charges had been filed.

“The FBI is currently investigating this incident,” Chicago police said in a statement.

CNN has reached out to the Federal Bureau of Investigation (FBI) as well as the Air Hostesses Association representing United Workers.

Top photo: The United Airlines terminal at Chicago O’Hare International Airport is shown in this file photo. (Joshua Lott/AFP/Getty Images)