(IDEX Online) - Eight suspects have been arrested over an attempted gem heist in which smoke bombs caused panic among the crowds at St Mark's Square, in Venice.Visitors feared a terror attack was under way when the raiders struck in March 2017.It soon became clear the confusion was a cover for an attempted robbery at a high-end jewelry store.A tourist alerted police and the raiders - at least one of them armed (see pic) - fled empty-handed. A three-year investigation by Europol, the European law enforcement agency, has now resulted in eight arrests, in Austria, Estonia and Finland.The same suspects were allegedly involved in robberies at jewelry stores in Corsica and Austria, in 2016 and 2017, in which over $1.2m of goods were stolen.