UEFA have acknowledged Holland's black players were the victims of racist abuse during a training session in Krakow.
Members of Bert van Marwijk's European Championship squad were allegedly subjected to monkey chants during an open training session on Wednesday, with captain Mark van Bommel branding the incident "a real disgrace" on Thursday.
Having initially been satisfied by the Dutch Football Association's belief that the abuse was not racially motivated, UEFA announced on Friday morning they had been made aware of "isolated incidents of racist chanting".
European football's governing body said in a statement: "UEFA has now been made aware that there were some isolated incidents of racist chanting that occurred at the open training session of the Dutch team.
"UEFA has not yet received any formal complaint from the KNVB."
UEFA vowed to act should there be a repeat. Their statement continued: "Should such behaviour happen at further training sessions, UEFA would evaluate the operational measures to be taken to protect the players.
"UEFA has a zero-tolerance policy when it comes to discriminatory behaviour and has given the power to referees to stop matches in case of any repeated racist behaviour."
Press Association Sport understands UEFA's stance changed following lobbying from the FARE (Football Against Racism in Europe) network.
The chief executive of European football's leading campaign group against racism, Piara Powar, told Press Association Sport earlier: "Van Bommel has no reason to invent such a claim.
"It's quite clear it happened.
"And if there's some confusion within the governing bodies, the KNVB or UEFA, then that's regrettable.
"In our view, the incident took place."
He added: "If the captain says, 'My team-mates 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."
The Dutch FA were not immediately available for comment but the BBC were reporting that they would not make a formal complaint and considered the matter closed.
UEFA were satisfied on Wednesday by claims the abusive chanting from the stands was actually a protest against the fact Krakow had not been made one of the host cities for Euro 2012.
Another theory put forward was that Wisla's supporters did not want their stadium being used by anyone but their own club and were simply booing the Dutch players.
The problems reportedly occurred when players began Wednesday's training session by doing laps of the pitch only to be greeted at one end of the stadium with monkey noises and loud jeers.
The abuse was said to be bad enough for the squad to move their equipment and training drills as far away as possible from that area.
Van Bommel told anyone who denied it was racially-motivated to "open your ears", adding: "If you did hear it, and don't want to hear it, that is even worse."
Holland were due to travel to Kharkiv, Ukraine, on Friday where they will hold a press conference ahead of their Euro 2012 Group B opener against Denmark on Saturday.
There were already fears over racism at this summer's tournament, with BBC's Panorama programme last week highlighting the problem at Krakow's two major clubs, Wisla and Cracovia, as well as in Ukraine.
UEFA president Michel Platini said on Wednesday referees would halt or even abandon matches if there was serious racism from the stands during Euro 2012.
Mario Balotelli - whose Italy side are also based in Krakow - had threatened to walk off in protest if he was racially abused during games but Platini warned any player who did so would be yellow-carded.
The families of two of England's black players, Alex Oxlade-Chamberlain and Theo Walcott, have already decided against travelling to the tournament because of the potential problems.
Powar called on teams to play their 'open' training session behind closed doors if necessary.
He said: "Public displays of intolerance like this - xenophobia, anti-semitism and racism - can't be allowed to go on.
"If that means playing behind closed doors and closing down that whole open-training system then I think that needs to be done."
Powar said on Wednesday he was more concerned about Euro 2012 than any previous tournament because of the well-documented problems with racism and anti-semitism in Poland and Ukraine.
He added on Friday: "It's a great shame for this to happen on the eve of the tournament."
Action UEFA could take is understood to include ejecting fans as well as tighter security checks and increasing steward numbers.