The interviewees are understood to have included Clattenburg plus assistant referees Michael McDonough and Simon Long and fourth official Michael Jones.
The interview process was expected to be completed today, enabling a decision on whether any action should be taken by the FA to be made early next week.
Chelsea submitted a dossier of evidence to the FA containing signed witness statements from players, who allege Clattenburg used a term understood to have been interpreted as racist during the Premier League match against Manchester United on October 28.
Newcastle United fan Clattenburg, meanwhile, has decided not to referee a match for a second consecutive weekend while the investigation is ongoing.
The Metropolitan Police has also launched an investigation following a complaint lodged by the Society for Black Lawyers, based on reports of the incident rather than any evidence.
Source: Newcastle United Mad
Source: FOOTYMAD
