Operations have resumed at a terminal at Chicago's O'Hare International Airport after a portion of it was closed briefly while security personnel investigated a suspicious package.

City Aviation spokeswoman Karen Pride says the doors to the upper level at Terminal 2 were sealed Thursday afternoon by the Transportation Security Administration. Minutes later airport officials tweeted that the terminal has been reopened to travelers.

Officials did not immediately say what was in the package that caused the lockdown.

While operations at the terminal were suspended, passengers headed there were directed to Terminal 1 for security screenings.

Delta, Air Canada and US Airways are among the carriers operating out of Terminal 2.