The airport said the departures area of Terminal 1 was cleared at around 10:20 a.m. (0920GMT, 5:20 a.m. EDT) as "a standard precautionary measure."
Police said they were questioning a man about the find.
Just after noon, the airport said the terminal was being reopened. A spokeswoman said 11 flights due to leave Wednesday morning had been delayed by the bomb scare.
There was no disruption to arriving flights, and the airport's other two terminals remained open.