Four 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 told PA that the operation to identify individuals involved in the abusive chanting was still ongoing.
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.
A spokeswoman for the ministry said: “The operation of Sofia metropolitan police is still ongoing. At this stage four males are detained.
“The work is ongoing to establish whether they were involved in this incident. The operation continues during the day.”
The spokeswoman 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.
Under the UEFA regulations, the BFU could face a full ground closure for their next competitive home match and a fine of 50,000 euros, but Aleksander Ceferin, the president of European football’s governing body, spoke on Tuesday about ‘waging war’ on racism.
Under Article 14 of UEFA’s disciplinary code which relates to racism, there is scope to impose a tougher sanction such as points deduction or even disqualification “if the circumstances of the case require it”.
FIFA president Gianni Infantino also suggested any penalties imposed would be extended worldwide. He said football needed “new, stronger and more effective ways to eradicate racism in football“ and called for life bans from stadiums for any individuals found guilty of racist behaviour.
PA
