Racism reared its ugly head yet again as players from the Dutch squad were subjected to monkey chants from the crowd in an open training session at Krakow, Poland.
Several hundred people targeted black players from Holland, who were undergoing a training session at the Stadion Miejski, the home of Wisla Krakow, ahead of their match against Denmark on Saturday.
England are supposed to hold open practise sessions on Friday at the same ground.
Dutch captain Mark Van Bommel, incensed by the abuse asked the players to move towards the far end of the ground and away from the crowd.
"It is a real disgrace especially after getting back from Auschwitz that you are confronted with this," Van Bommel said. "We will take it up with UEFA and if it happens at a match we will talk to the referee and ask him to take us off the field."
The Dutch side visited Auschwitz, the concentration camp, on Wednesday.
The problem occurred when the Dutch side started taking a lap around the stadium, with a few hundred supporters jeering and making monkey chants. When the Netherlands team made another lap, the chants continued again, and they then decided to curtail that part of the session. "At least now we know what we can encounter," Dutch coach Bert van Marwijk said. "Very atmospheric," he added sarcastically.
Van Bommel, clearly unhappy with the situation responded strongly when some journalists said they had not heard the chants. "If you did hear it and did not want to hear it, that's even worse," the Dutch midfielder said. "You need to open your ears."
UEFA, however, immediately denied the claims, saying they had heard from the Dutch officials it was not racially motivated. Instead, UEFA said it was a group of supporters just booing the team, because they did not want another team, other than the home club Wisla Krakow, using the facilities. It is also being said they were simply booing, because Krakow was not made one of the host cities.
UEFA later backed away from their earlier claims, suggesting they had received word about "isolated incidents" of racist chants, but remarkably the governing body said they would investigate the issue only if there was a repeat of the abuse a second time.
"Should such behaviour happen at further training sessions, UEFA would evaluate the operational measures to be taken to protect players," UEFA said in a statement.
Piara Powar, executive director of Football Against Racism in Europe said UEFA needed to act. "Van Bommel has no reason to invent such a claim," Powar said. "We would side with Van Bommel. It's quite clear it happened.
"If the captain says, 'My teammates were racially abused, I heard it, I was there at the ground level', then one expects any FA to back the captain. We're very clear with UEFA that any incident of this kind needs to be looked at."
It is a bad start to the tournament that has already been garnering all the wrong attention, with several fearing racist abuse. While the authorities have rubbished chances of racism during the tournament, the Dutch experience will further increase fears of racism being the focal point of soccer's second biggest event.