Police in Switzerland, France, Spain and Italy carried out raids early on Tuesday morning as part of investigations into three nights of violence surrounding the Group of Twenty summit in the German city.
Prosecutors in Hamburg said the raids were chiefly focused on events in the city's Elbchaussee street on the night of July 7th. Video evidence had helped them identify several suspects.
A 27-year-old man in the Swiss canton of Aargau was among those questioned. His apartment was searched as was a nearby left-wing culture sentence, cantonal police said.
The suspect was said to be the son of Matthias Hüppi, a well-known former sports presenter with Swiss national broadcaster SRF, according to unconfirmed reports by Switzerland's Blick newspaper.
"Investigations are ongoing. A decision on criminal proceedings will be made when those investigations are completed," Hamburg chief prosecutor Nana Frombach told Blick.
The man has now been released.
Some 200 demonstrators were held after the July 7th protests in Hamburg which saw cars burned and close to 500 police attacked.