The Portuguese Football Federation are the latest national governing body to be investigated by UEFA.
It has been brought to UEFA's attention that a Portuguese supporter attempted to invade the Stadio Narodowy pitch during their country's 1-0 win over the Czech Republic on Thursday.
"UEFA has opened disciplinary proceedings against the Portuguese Football Federation (FPF) for the inappropriate behaviour of their supporters – attempted invasion of the field of play by a fan – at the UEFA Euro 2012 quarter-final match against the Czech Republic in Warsaw on Thursday," read a statement.
"The UEFA Control and Disciplinary Body will deal with the case on Monday."
The English FA was recently fined £4,000 for a similar offence.