Borussia Dortmund were forced to evacuate their main offices on Wednesday after receiving a "suspicious envelope with white powder", which turned out to be icing sugar.
Emergency services were called to the building in Rheinlanddamm after a number of Dortmund employees noticed a white substance, with Ruhr Nachrichten reporting that 40 firemen were called to the scene.
Tests were conducted in a mobile laboratory, which determined that the substance was harmless.
Dortmund confirmed the details of the incident via their Facebook page, adding that the offices were reopened roughly one hour later and all employees returned to work safely.
"Big thanks to the Dortmund fire department!" the club said. "We received a suspicious envelope with white powder today. For security reasons, we evacuated the building completely for about one hour.
"The powder was analysed twice in a mobile chemical laboratory. We got the result at 17:20: icing sugar! All Borussen are now back at work."
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