Bomb and arson officers were at O'Hare Airport's Terminal 3 Friday morning after an unauthorized semi truck was in front of the upper level of the terminal, authorities confirmed. Police said the officers were at the scene as a "precautionary measure" until the truck was removed. It was not immediately clear why the truck was parked in front of the terminal, but no driver was inside when authorities arrived, police said. Police dogs investigated the vehicle and it was eventually towed away.