Planned Airplane Bombing

The Federal Prosecutor's Office in Karlsruhe said in a statement that suspects had convinced an airport employee with security access to smuggle a suitcase full of explosives onto a passenger plane.

"During the summer, several suspects made contact with an individual who had access to the security-restricted zone of an airport," said a statement from the federal prosecutor's office.

The plan, however, fell apart when the unidentified suspects failed to reach agreement with the airport employee on the payment he was to receive. It was not clear if the helper was someone employed by the airport, an airline or a subcontractor.

Prosecutors have questioned six suspects they believe were involved in bomb plot, which reportedly was to take place at Frankfurt airport, a hub of international air traffic.

"With the exception of one suspect who is in prison for another offense, the other suspects were released on Saturday," the statement said.

Police also searched nine houses in the German states of Rhineland-Palatinate and Hesse over the weekend.

Suspected of belonging to terrorist organization

According to the prosecutor's office, the suspects had made contact several times with members of an unknown group without coming to an agreement on the size of the fee for smuggling the suitcase onto the plane.

The prosecutor's office gave no details about the nationality of the suspects, nor would they reveal the planned timing of the attack.

An aircraft belonging to the Israeli airline El Al may have been targeted, reported Die Welt daily. The airline has been a target of Islamic terrorists for decades and its planes are accompanied by armored police vehicles at some airports.

New reports won't affect security warning

Frankfurt is a busy hub for many flights to Israel, as well as the US, Great Britain and other potentially targeted countries. Some 60,000 passengers have to pass through security checks each day.

"With 60,000 passengers every day, 100 percent security isn't possible," said Germany's Interior Minister Wolfgang Schäuble last week, reported AP.

The German government on Monday said it would not increase its security warning in light of the new investigation.

"We always have to count on there being groups of people who are considering real plans," an interior ministry spokesperson said in Berlin.

Germany must remain vigilant

Germany was shaken in the summer after it was discovered that homemade bombs hidden in suitcases failed to explode on two regional passenger trains in an apparent bid to copy the devastating train bombings in Madrid and London.

Two Lebanese men have been charged with planting the devices on trains heading for the western cities of Hamm, near Dortmund, and Koblenz, on July 31.

Germany's federal prosecutor Monika Harms warned last week that although no attack had taken place on German soil recently, the apparent peace "could be deceptive" and the country must remain vigilant.