Germany’s interior minister has revealed that a suspicious package found at an airport in Namibia was part of a security test.

A German police officer patrols Frankfurt airport while the country remains on high alert.

A German police officer on patrol as the country remains on high security alert

Thomas de Maiziere said the fake bomb was designed by an American firm to test measures at the airport, but was not organised by the German government.

The detonator, clock and batteries were left in a suitcase to be loaded onto an LTU/Air Berlin flight to Munich on Wednesday.

Namibian police conducting routine checks siezed the luggage shortly before it was put on a plane at the international airport in Windhoek.

Passengers and crew were taken off the plane and faced a six-hour delay before arriving safely in Munich.

Germany’s Federal Crime Office, the BKA, said an X-ray of the suitcase revealed batteries wired to a “detonator and a ticking clock”.

No explosives were found in the suitcase and at no time was there any danger to passengers

German interior minister Thomas de Maziere

After examining the case they concluded it was a “real test suitcase” designed by a firm that produces alarm and detection systems.

However, there had been some confusion over whether the fake bomb was a test or not.

Some sources reported that the package carried a label highlighting that it was part of a security operation.

Mia Davids, a public relations officer for the Namibian Airports company said that the detonator was not part of a drill.

Sky News security editor Sam Kiley said at the time he felt the discovery was unusual because detonators are usually the hardest things for terrorist groups to find.

He said explosives were easier to locate – particularly in Namibia, due to the country’s mining industry.

German interior minister Thomas de Maiziere

German interior minister Thomas de Maiziere

The detonator, which did not contain explosives, was found on the same day that Mr de Maiziere decided to put the country on high security alert.

Security measures at airports and train stations were stepped up following the interior minister’s announcement that there are “concrete indications of a series of attacks planned for the end of November”

The BKA has sent officers based in South Africa to Namibia, a former German colony, to aid the investigation.

French and British security services have also been put on a high state of alert.

Last month, authorities discovered two US-bound parcel bombs originating from Yemen, one of which went through Cologne airport in western Germany.

On November 2, an explosive device was posted to Chancellor Angela Merkel’s office in a suspected attack by Greek radicals.