Police in the western German city of Essen ordered a shopping mall in the center of town to stay closed on Saturday morning due to "concrete indications about a possible attack."
The shopping center and the adjacent parking lot stayed closed into the early afternoon as more than a hundred police officers searched the compound.
Police also boosted their numbers in the city's main train station, according to an official police Twitter account, although trains were still running.
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"The current investigation shows that the threat is only related to the shopping center" at Limbecker Platz, Essen police said in a statement.
Security officials were working "intensely" to discover more information, the statement added.
Germany is on high alert following major radical Islamist attacks in France and Belgium and after a failed asylum seeker from Tunisia drove a truck into a Christmas market in December, killing 12 people.