EU authorities said Thursday they will be on watch for a spike in customs fraud and human trafficking during the European football championship, as the bloc\'s border lies between hosts Poland and Ukraine. \"The challenge for border guards at events like Euro 2012 is the management of large passenger flows across the borders,\" said Gil Arias Fernandez, deputy head of European Union border agency Frontex. \"Our risk analyses say that criminal networks may try to hide the smuggling of cigarettes, petrol, et cetera, as well as stolen vehicles, taking advantage of the increased traffic at border crossing points,\" he told reporters. \"There is also a risk of concealing the traffic of human beings in the midst of these flows, mainly women for prostitution purposes,\" he added. On Monday, Poland announced that during the championship, which runs from June 8 to July 1, it would reintroduce controls on its borders with EU neighbours Germany, the Czech Republic, Slovakia and Lithuania. Such checks were dropped in December 2007 when Poland joined Europe\'s travel-smoothing Schengen zone, which now comprises 26 countries, including several non-EU members. Schengen rules allow members to resume border controls in certain cases, notably when large numbers are expected to flock into a country -- and Euro 2012 is expected to draw more than a million people. Germany took such a step when it hosted the World Cup in 2006, a move followed at Euro 2008 in Austria and Switzerland. Euro 2012 is very different from those tournaments, which were well within western Europe, because the tightly-controlled eastern rim of the EU runs between Poland and Ukraine. \"This is a first in European history, with a sports event held in two countries with the EU frontier between them,\" underlined Lieutenant Colonel Piotr Patla, head of the Polish Border Guard\'s management department. Former communist Poland joined the EU in 2004 and its border controls with ex-Soviet Ukraine were further beefed up when it entered the Schengen zone. During Euro 2012, Poland aims to keep border crossings for fans as fluid as possible while also ensuring that EU entry and security rules are respected. Resuming internal Schengen checks is therefore seen as a way to balance out a lighter touch than usual on the EU border with Ukraine.