BERLIN - A person trespassed a security checkpoint at the Cologne-Bonn airport in western Germany on Monday, prompting police to declare a state of alert that brought all flights to a halt, local media reported. Police are searching for the person and ordered all planes that were on their way to take off to taxi back to the gates, the Koelner Stadt-Anzeiger newspaper reported online. The federal police, which is responsible for airport security, could not be reached for comment. Local police declined to comment. A spokeswoman for the interior ministry in the state of North Rhine-Westphalia, where Cologne is based, said she was not aware of the incident.