Bulgarian authorities have arrested six soccer fans linked to making racist gestures, including Nazi salutes, during a European Championship qualifying match against England.
Bulgarian fans also made monkey noises at England's black players during the October 14 game, which was halted twice in an effort to stop the racist abuse. England won the game in Sofia 6-0.
Bulgaria supporters in the crowd were also seen doing Nazi salutes and holding up shirts with the UEFA logo and the text "No respect" -- a reference to UEFA's "Respect" campaign aimed at curbing racism in the sport.
"So far six people have been detained and another three are being actively sought," said Sofia police chief commissioner Georgy Hadzhiev, adding that a total of 15 people had been implicated in the racist abuse of England players.
The Interior Ministry said in a statement that any evidence collected will be handed over to prosecutors.
The president of the country's soccer federation, Borislav Mihaylov, resigned on October 15 and Bulgarian special-police forces have raided the federation offices.
Mihaylov’s resignation came hours after Prime Minister Boyko Borisov earlier in the day urged him to step down "immediately."
It was "inadmissible that Bulgaria...is associated with racism and xenophobia," the prime minister wrote on Facebook, adding that the government would cut all ties with the soccer federation until Mihaylov resigned.
Bulgaria coach Krasimir Balakov, who initially said he hadn't heard any racist abuse during the game, has apologized to the England team.
"I strongly condemn and reject racism as a norm of conduct that contradicts modern human relations," Balakov said in an e-mail on October 15.
"I want to say something very clear: given that there have been insults on such a basis, I, as a coach of the national team, apologize to the English footballers and all those who feel hurt."
European soccer's ruling body, UEFA, has opened disciplinary proceedings against Bulgaria over the racist behavior.
British Prime Minister Boris Johnson has condemned the "vile" incidents.
"This stain on football is not being adequately dealt with," Johnson's spokesman said on October 15. "Racism and discrimination must be driven out of football once and for all."