The Football Association's disciplinary unit has interviewed Everton defender Mason Holgate and Liverpool forward Roberto Firmino as part of the investigation into alleged racism during this month's FA Cup third round tie at Anfield, sources have told ESPN FC.
The FA is investigating claims by Holgate that he was racially abused by Firmino after shoving the Brazilian into advertising hoardings at the side of the pitch during the first half of Everton's 2-1 defeat.
While no timescale has been put on the investigation, FA sources have confirmed the probe is making progress and that witnesses, including match officials and players from both teams, have been, or are in the process of being, interviewed by the governing body's disciplinary unit.
Referee Bobby Madley triggered the investigation by submitting a match report to the FA, detailing the incident and Holgate's allegation, prompting the FA to confirm that it would investigate the incident.
An FA statement, issued earlier this month, said: "The FA can confirm that referee Bobby Madley was made aware of an allegation during the Liverpool versus Everton game at Anfield last night and has subsequently reported this to The FA, which will now begin making enquiries into the matter."
Although Friday will mark three weeks since the Liverpool-Everton tie, the FA are determined not to set a timeframe on potential charges being issued, with sources insisting that a thorough investigation is the priority, rather than a need to move swiftly, due to the serious nature of the allegations.
When Luis Suarez was charged with racially abusing Manchester United defender Patrice Evra in 2011, it took the FA more than four weeks of investigations before charging the Liverpool forward.
Suarez then had to wait another month before being issued with an eight-match suspension and £40,000 fine after being found guilty of the charge.