Updated

A suspicious package found in a Namibian airport near bags bound for Munich was a device designed to test security and didn't contain explosives, officials said Friday. One aviation official said the test was conducted by Namibian police.

Wednesday's discovery of the package at Windhoek airport came the same day that Germany raised its terrorist alert level.

German security experts determined that the bag was a "real test case" made by an American firm to test security measures, German Interior Minister Thomas de Maiziere told reporters Friday.

"Most important is that there were no explosives in the bag and there was never any danger to the passengers," de Maiziere said.

Namibian police confirmed his report but did not say who may have been testing security at Windhoek. An Air Namibia official, however, said it was Namibian police themselves who had conducted the test. The official spoke on condition of anonymity because it was a police matter.

Concern that international flights were once again being targeted by terrorists rose last month when two mail bombs were discovered being sent on cargo planes from Yemen to the U.S. One of them went through a German airport before being found in Britain.

The Windhoek incident came as Germany already was on edge after de Maiziere raised the country's terrorist threat level, saying intelligence services had received a tip from an unspecified country about a suspected attack planned for the end of November.

In comments published Friday in the Bild newspaper, Germany's federal police president said the terrorist threat facing the nation was "more serious than ever before."

While urging against "panic or hysteria," Matthias Seeger said "on a scale of one — no danger — to 10 — acute danger of an attack — we are currently at 9. Therefore we need to be particularly alert."

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Jenny Gross in Johannesburg and Patience Nyangove in Windhoek contributed to this report.