O'Hare International Airport reopened Terminal 1 just after 11 a.m. Wednesday after a portion of the terminal was evacuated because of an unattended bag, police said.
The bag was found at about 9:30 a.m. on the upper level of the terminal, police said. An all-clear was given after the Chicago Police Bomb Squad removed the bag.
"The incident at O'Hare International Airport Terminal 1 has been secured by the Chicago Police Department," the Chicago Department of Aviation said, noting police will continue their investigation.
Inner roadways to Terminal 1 on both the upper and lower levels were closed following the evacuation, and transit service to the terminal was suspended. A portion of the ticketing area and baggage claim were evacuated.
"Transportation Security Administration personnel at O’Hare International Airport discovered an unattended item located in a Terminal 1," the TSA said in a statement. "To ensure the safety of the traveling public, the terminal was immediately evacuated. Local law enforcement responded and are currently working to clear the item."
United Airlines said in a statement it is closely monitoring the situation and cooperating with authorities.
"We encourage our customers traveling out of O’Hare to check the status of their flight on united.com or on the mobile app and allow extra time for security screening," the airline said.
Backups were seen outside the airport, and some passengers took to social media with worries about making their flight. After the all-clear, all airlines were reporting normal flight operations.