HEBRON, Ky. (AP) -- Baggage screeners saw what looked like a gun in an X-ray of a carry-on bag, and some flights departing Cincinnati-Northern Kentucky International Airport were held for about two hours Sunday during the search for the passenger and the weapon, officials said.
The passenger was not located and no weapon was found, said Christopher White, a Transportation Security Administration spokesman in Atlanta.
Flights were only allowed to depart during the search if passengers had boarded prior to the TSA screeners' discovery about 7:15 a.m. of what they believed was a gun in the X-ray of a carry-on bag, White said.
The passenger had already picked up the bag and left the checkpoint when screeners noticed the image, White said.
The TSA is investigating the incident and as of Sunday night hadn't determined how the passenger made it through the checkpoint before the image of the bag was noticed, White said. He wouldn't elaborate on how the investigation is being conducted.
One of the airport's three terminals and three of its five concourses were closed in the search, airport spokesman Ted Bushelman said.
Officials don't believe the passenger boarded a plane because the areas were closed down and people were forced to leave, White said.
The areas reopened about 9:15 a.m. and nothing suspicious was found when the passengers went through security again, White said.
''By clearing the concourse and searching the concourse, we can ensure the concourse is secure and free of weapons,'' he said.
Bushelman said thousands of passengers were affected, but he couldn't provide the exact number.
He did not know how many Delta, Comair, Northwest and Continental departing flights were delayed. US Airways, American and United were not affected by the partial shutdown, Bushelman said.
On a few incoming flights, passengers were forced to stay in the planes after they landed until the situation was resolved, he said.
It took 90 minutes to re-screen the passengers who were forced to leave during the search and another 45 minutes to check in the passengers who were delayed outside the terminal, Bushelman said.
All flights were back on schedule by early Sunday afternoon, he said.