Liverpool have collected "substantial" evidence after an alleged spitting incident directed at Manchester City backroom staff during their Premier League match on Sunday.
The Reds have gathered a number of witness statements from people seated around the dugout area and are working with City staff to collect more evidence and unredacted video footage.
The club's official sanctions process can result in a life ban, while there is also the potential for criminal charges.
"Following a complaint of a serious alleged incident near the dugout area at Anfield during the second half of Sunday's game against Manchester City, we are conducting a full investigation, working with all relevant parties including Manchester City, to gather evidence from individuals who witnessed the incident as well as analysing all available video footage," a Liverpool spokesperson said:
"The evidence collected to date is substantial and, if requested to do so, will be handed to Merseyside Police given the potential for criminal charges.
"Anfield is our home and we will ensure it is a safe, enjoyable environment for everyone attending and will not allow unacceptable isolated behaviour to impact on our club's values and principles."
City manager Pep Guardiola said that he was not aware of the incident at the time but was notified by his staff later.
"I don't know what happened," Guardiola told Sky Sports after the game.
"I heard something from the crowd - something not nice to staff. But I don't know what exactly. I didn't see the images.
"I'm pretty sure that if it happened, I'm sure Liverpool will take measures about this person. Liverpool are much greater than this behaviour.
"Nothing will change my admiration for this club.
"It was the same story two, three years ago when we came here and they destroyed our bus - it is certain people, not just Liverpool."
Australian Associated Press