Six men have been detained by Bulgarian police in relation to the racist abuse of England players on Monday night.
The Bulgarian ministry of the interior said 15 individuals suspected of involvement in the abusive chanting had been identified .
England's black players were targeted throughout the match, and the Bulgarian Football Union has been charged by UEFA over the racist behaviour of its fans.
"We do not tolerate such behaviour," said Bulgaria Ministry of the Interior commissioner Georgi Hadzhiev.
A spokesperson also confirmed that special forces from the ministry's general directorate for combating organised crime had raided the BFU offices on Tuesday.
The BFU's president, former national team goalkeeper Borislav Mihaylov, announced his resignation in the wake of Monday night's racist chanting.
Hristo Stoichkov, who scored 37 goals for Bulgaria, said
Meanwhile, FIFA president Gianni Infantino has demanded "new, stronger and more effective ways to eradicate racism in football".
Infantino called for worldwide life bans for those found guilty of racist behaviour.
He said: "I call on all football governing bodies to join us and think together of new, stronger and more effective ways to eradicate racism in football.
"As a starting point, I suggest that all competition organisers enact regulations which envisage life bans from stadiums for those who are found guilty of racist behaviour at a football match. FIFA can then enforce such bans at a worldwide level."