UEFA has 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 yesterday branding the incident "a real disgrace".
Having initially been satisfied by the Dutch Football Association's belief that the abuse was not racially motivated, UEFA announced this 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."