Police ordered a shopping centre in western Germany not to open on Saturday after receiving credible tips of an imminent attack.
The mall and adjacent car park in the city of Essen stayed closed as about 100 officers - many armed with machine pistols and bullet-proof vests - positioned themselves around the complex to prevent anyone from entering.
Several officers scoured the interior to bring out early morning cleaning staff.
"As police, we are the security authority here and have decided to close the mall," police spokesman Christoph Wickhorst said, adding that they had been tipped off by other security agencies late on Friday.
He refused to give further details because of the ongoing investigation.
The shopping centre at Limbecker Platz square was closed for the entire day.
The mall is one of the biggest in Germany with more than 200 stores and attracts up to 60,000 people on a regular Saturday, according to its website.
In 2016, three people were injured in an attack on a Sikh temple in Essen by radicalised German-born Muslim teenagers.
Germany has been on edge following a series of attacks in public places over the past year.