Metropolitan Police are investigating a poster denouncing the Saudi ownership of Newcastle by Crystal Palace supporters for racism.
Before the 1-1 draw between the sides at Selhurst Park, the graphic banner was held up, criticizing the Premier League's owners and directors' test and citing some of Saudi Arabia's human rights issues.
Despite the Saudi sovereign wealth fund being the majority financier, the Premier League gave the go-ahead for a £305 million ($420 million) takeover earlier this month.
Newcastle overturned a demand for fans not to wear Arab-style clothing to celebrate the takeover before the game.
"Those who wish to support the club by wearing appropriate culturally-inspired clothing should feel free to do so as they see fit," the Magpies said in a statement.
"Neither the club nor its new owners were offended by attire worn, and appreciate the overt statements of support and acceptance by our great fans."