Borussia Dortmund's Jadon Sancho and Achraf Hakimi as well as Schalke's US midfielder Weston McKennie called for justice for George Floyd who died last week after a white policeman in Minneapolis held his knee on the handcuffed man's neck for several minutes.
Borussia Moenchengladbach's Marcus Thuram took a knee after scoring to echo the gesture by former NFL quarterback Colin Kaepernick, whose decision to do so during in 2016 sparked outrage.
The first three are being reviewed by the DFB's Control Body which is following guidelines from the sport's lawmakers, the International Football Association Board.
Despite the decision DFB president Fritz Keller praised the four individuals' protests.
"I have huge respect for players who take a stance and show their solidarity. We need responsible players like them and I am proud of them," he said.
"From a moral standpoint, I completely understand their actions on the weekend. There is no one who isn't moved by what has happened in the USA."