Police guard in front of a shopping mall in Essen, Germany, Saturday, March 11, 2017. Police have ordered the shopping mall in the western German city of Essen not to open after receiving credible tips of an imminent attack. The shopping center and the adjacent parking lot stayed closed Saturday morning as over a hundred police officers searched the compound. (Bernd Thissen/dpa via AP)

Police guard in front of a shopping mall in Essen, Germany, Saturday, March 11, 2017. Police have ordered the shopping mall in the western German city of Essen not to open after receiving credible tips of an imminent attack. The shopping center and the adjacent parking lot stayed closed Saturday morning as over a hundred police officers searched the compound. (Bernd Thissen/dpa via AP)

BERLIN (AP) — Police ordered a shopping mall in the western German city of Essen not to open Saturday after receiving credible tips of an imminent attack.

The shopping center and the adjacent parking lot stayed closed as about 100 police officers — many armed with machine pistols and bullet-proof vests — positioned themselves around the compound to prevent anyone from entering the mall. 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 late Friday by other security agencies. He declined to provide further details, but police later said there had been concrete indications for an attack on Saturday.

Essen police said later that they were questioning a man, and had searched his apartment in nearby Oberhausen.

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A second man was detained at an internet cafe in Oberhausen in the afternoon and police also increased their presence at a mall, the Centro, in that city, the German news agency dpa reported.

In Essen, the downtown mall at Limbecker Platz square will be 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 the shopping center’s website.

In 2016, three people were injured in an attack on a Sikh temple in Essen by radicalized German-born Muslim teenagers.

Germany has been on the edge following a series of attacks in public places over the past year. When a man went on a rampage with an axe on Friday night at Duesseldorf’s main station and injured 10 people, about 600 police officers were deployed to the scene, even though it later turned out that he had no links to extremists, but was suffering from psychological problems.