The blast occurred about 200 metres (yards) from the centre in the Bavarian town of Zirndorf, where police were on the scene.
"There is no indication at the moment that a bomb was detonated in the suitcase," police said in a statement.
Suspected bomber killed in German bar blast
"It is possible it was a spray can inside the suitcase that caused the explosion. No one was reported injured."
The incident occurred in Bavaria, where authorities are on edge after three attacks in a one-week period.
On Sunday, a Syrian asylum seeker with suspected links to the Islamic State group blew himself up near a music festival in Ansbach, wounding 15 people.
Nine people were killed in a shopping centre shooting spree in Munich on Friday, just six days after four passengers on a train and a passer-by were wounded in an axe attack in Wuerzburg.
Bavaria has been a gateway for the influx of migrants and refugees to Germany, which saw a record 1.1 million people arrive last year.
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