Tuesday’s UEFA Champions League match between Paris Saint-Germain and Istanbul Basaksehir was supposed to be anticlimactic, as an expected win at home for PSG against the overmatched, already-eliminated Turks would send Neymar and Co. into the knockout stage.

Instead, an incredible scene played out at the Parc des Princes in the French capital, with both teams eventually walking off the field in the first half after the fourth official allegedly directed racist language toward one of Istanbul’s assistant coaches.

According to the visitors’ official Twitter feed, assistant coach Pierre Webo, who is black, was on the receiving end of the exchange. French outlet L’Equipe said Romanian fourth official Sebastian Coltescu identified Webo to the center referee as “negru,” the Romanian word for black.

Webo objected immediately. Istanbul’s players, led by veteran former Chelsea forward Demba Ba, made it clear that they didn’t appreciate the comment. Ba was seen confronting the entire refereeing crew, demanding to know why Coltescu why referenced Webo’s skin color at all:

Webo was red-carded in the 14th minute, setting off the incident. Players and staff on both teams stayed on the field for another nine minutes before eventually retreading to their respective dressing rooms.

After reportedly agreeing to restart the match with a different fourth official, the game was eventually called off after Istanbul’s players refused to continue with Coltescu as the video assistant referee. PSG’s players declined to continue in a show of solidarity.

UEFA, European soccer’s governing body, said in a statement released after midnight local time that it would conduct a thorough investigation. It also announced that the remainder of Tuesday’s game would be made up on Wednesday “with a new team of match officials.”

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