The German FA (DFB) has opened investigations against Borussia Monchengladbach after some of their fans insulted referee Bibiana Steinhaus during the 2-1 win against Hertha Berlin on Saturday.
Steinhaus, the only female referee in Germany's upper tier, was subject to the abuse of Gladbach supporters, especially after she disallowed a 54th-minute equaliser following intervention from the video assistant referee (VAR).
When Gladbach were awarded a penalty with the help of VAR, the abuse continued despite the decision going the hosts' way.
On Monday, the DFB opened investigations against the Bundesliga club, kicker reported.
"As a club, we must apologise to Bibi Steinhaus. For me, she is an excellent referee," Gladbach sporting director Max Eberl said on ZDF TV. "I just don't hope that I was the role model for the fans chanting that bulls---."
Last month, Eberl was fined €5,000 by the DFB after insulting Hoffenheim coach Julian Nagelsmann when they clashed on the touchline during the sides' 3-3 draw.