( CNN ) -- A suspicious piece of luggage that was about to be loaded onto a plane at Windhoek Hosea Kutako International Airport in Namibia contained no explosives , a spokeswoman for the airline said Thursday . `` Air Berlin has confirmed that there was no explosive material in the laptop bag found in Namibia , '' Sabina Teller , spokeswoman for Air Berlin , told CNN . `` The luggage was found in the airport , at no point was on the plane . It had no luggage label so it was impossible to know where it was going , which company it was supposed to fly with or who it belonged to . '' The laptop bag , found Wednesday morning among the luggage being loaded onto flight 7377 to Munich , Germany , contained a functioning electronic clock with wiring attached , suitable for use in a bomb , sources close to the investigation told CNN Thursday . The sources asked not to be identified because of the sensitivity of the investigation . The bag was discovered at a luggage screening point by security officials , who then notified the Namibian police explosives unit . After it was verified that the bag contained no explosives , passengers were asked to get off the plane to identify their luggage , but no one claimed ownership of the laptop bag , the source said . The flight resumed about six hours later to Munich , but some cargo was held back for investigation by officials from Namibia , Germany and the United States . The Namibia Airports Company , which runs the Windhoek airport , said the item was found at the luggage screening point prior to loading , though it did not specify whether the item was supposed to be loaded onto the Air Berlin flight . The 296 passengers and all the bags on the flight were subjected to additional security checks before the flight took off . It landed safely in Munich after a six- or seven-hour delay , said Air Berlin spokeswoman Silke Manitz . Germany raised its threat level on Wednesday , saying concrete evidence had emerged of a possible attack planned there later this month and of persistent efforts by Islamists to attack it . A senior German counterterrorism source told CNN on Thursday that the German Interior Ministry warning was linked to recent threats to the country from al Qaeda in Pakistan . Interior Minister Thomas de Maiziere said there was `` reason for concern but no reason for hysteria . '' `` Security authorities are considering three different threat scenarios by international terrorists , '' he said . `` Security authorities have been pursuing these indications for weeks with the highest intensity and proper sensitivity -- in closest cooperation with our international partners . `` Now further insights and facts relevant to danger have added themselves to these established insights , '' he said Wednesday . The `` new situation '' prompted authorities to raise the threat level . Last month , the United States issued a travel alert for Americans in Europe amid concerns that al Qaeda or related groups might be planning attacks similar to the 2008 massacre in the Indian city of Mumbai . CNN 's Laura Perez Maestro in London ; Ben Brumfield in Atlanta , Georgia ; Diana Magnay in Hamburg , Germany ; John Grobler in Namibia ; and Nkepile Mabuse in Johannesburg , South Africa , contributed to this report .
Suspicious bag found to contain no explosive . Bag contains batteries , wires and a running clock , sources say . The flight lands safely in Munich , six to seven hours late .