A German government minister has yesterday revealed that a fake bomb found on an Air Berlin flight in Namibia was manufactured in the U.S. to test airport security. It was not yet clear who had planted 'test suitcase', said German interior minister Thomas de Maziere, but the one fact they had established was that the device had been manufactured by a U.S. company that specialises in alarm systems. At no time were passengers' lives in danger. Mr de Maziere said: 'This company is a manufacturer of alarm and detection systems and these real test suitcases are built to test security measures.' The Transportation Security Administration (TSA) confirmed yesterday that it was working with the German and Namibian authorities 'to determine the origin of the device and the reason it was being transported on the plane'. The suitcase, which contained batteries connected to a detonator and a ticking clock, was intercepted by authorities at Windhoek airport on Wednesday night and sparked an international terror alert. The threat came amid heightened concerns of terrorist threats against Germany that prompted de Maiziere to raise the country's threat level even before the Windhoek incident. A German security spokesman said: 'Security officials are getting set for the state of emergency to last until the end of the yea. The spokesman added that the country's police force was facing 'its biggest challenge in the post-war history [of Germany]'. He added that the threat to civilians was not just restricted to Germany's biggest cities like Berlin, Hamburg and Munich - adding: 'So long as the Christmas markets are on, we have to expect attacks at any time, and we will protect the population with a visible presence on these markets.' Mr de Maiziere said intelligence services had received word of planned strikes by Islamist militants. Citing security officials, the mass-selling daily newspaper Bild said German police were seeking two Indian and two Pakistani militants already believed to be in the country. 'Their names and faces are unknown,' the paper said. Intelligence services believed the four militants were planning an attack between Monday and Thursday in the final week of November, the paper added. Pakistan-based militant Ilyas Kashmiri and senior al Qaeda figure Younis al Mauretani have both been linked with the threats to Germany.(The Daily Mail)