The Scottish Football Association (SFA) have given Aleksandar Tonev seven days to respond to an official complaint of alleged racism.
Tonev was under investigation with the SFA over an alleged racist comment made during Celtic's clash with Aberdeen last weekend.
The Bulgarian, who is on loan from Aston Villa, was reported to the governing body by Aberdeen after defender Shay Logan told referee Bobby Madden of the incident.
Following the investigation, the SFA have issued notice of the complaint to the 24-year-old and given him a week to respond.
"Aleksandar Tonev, Celtic FC, receives notice of complaint over alleged excessive misconduct," the SFA tweeted on Friday.
"Mr Tonev has until Friday 26th September 2014 to respond to the complaint."
The notice also confirmed the principal hearing date for the case will take place on Thursday October 9.
Tonev, who was making his debut in the match, has denied the accusations.comments