The players wore branded ankle support socks over official Nike socks, "breaching media and marketing regulations and the Fifa equipment regulations".
Fifa announced yesterday that so far all doping tests before and during the World Cup have been negative.
Since January 2018, a total of 2037 tests have been conducted, Fifa said. On average, every player from the four remaining teams has been tested four times since January, with some of tested up to eight times.