Borussia Dortmund's Bundesliga clash with Hannover on Saturday is set to go ahead despite the discovery of three explosive devices near the club's Signal Iduna Park.
German police have arrested a 25-year-old man after he was found to have sent anonymous tips about planned attacks to authorities. The man had buried a cache of explosives and weapons, including three bombs and was arrested in Cologne on Tuesday.
A police spokesman said: ''We can confirm that investigations relating to suspect explosive devices are under way in North-Rhine Westphalia.
''During a search around the Signal Iduna Park, three suspect explosive devices were discovered and diffused or made safe.
''Investigations into their functionality as well as the potential use of the discovered chemicals are continuing. Preliminary indications, however, do not point towards an acute threat to the public.''
During a search of the man's home, three suspicious objects and extensive written material on making chemical explosives were also discovered.
"The possible connection to an attempted extortion against a business in 2010 has been confirmed during the search," the statement added.