Liverpool have collected "substantial evidence" after Manchester City made a complaint alleging a home fan spat at their backroom staff in the first half of the 2-2 draw at Anfield on Sunday.
Liverpool are conducting a full investigation into the incident.
In a statement the club said witnesses had been interviewed while CCTV and video footage was being analysed.
"The evidence collected to date is substantial," Liverpool said.
"If requested to do so, [the evidence] will be handed to Merseyside Police given the potential for criminal charges."
It is understood any Liverpool fan found to have spat at Manchester City staff would face a possible lifetime ban from Anfield.