Nervous players and referees following official instructions to the letter may have caused a flurry of two red and 12 yellow cards in Tuesday's Cameroon versus Germany match -- a World Cup finals' record, FIFA said.
"It's not really for me to make a comment on the referees' performances. I think probably it might be a combination of ... rather nervous players and referees also following instructions to stand for no nonsense," FIFA spokesman Keith Cooper said on Wednesday.
Germany defender Carsten Ramelow was sent off in the 40th minute and Cameroon substitute Patrick Suffo in the 77th by Spanish referee Antonio Lopez Nieto in the group E match.
Twelve yellow cards were shown in another match on Tuesday between Senegal and Uruguay, again more than the previous record of 10.
There have been 158 yellow cards so far at this World Cup, an average of 4.4 per game compared with 4.0 at the 1998 World Cup and 4.5 at the 1994 tournament.
Seven red cards have been handed out. Referees were told by world soccer's governing body to clamp down, particularly on players faking injury at the month-long tournament that began on May 31 and ends with the final in Yokohama on June 30.