"Following a thorough investigation of this incident, any individuals found guilty of improper conduct will receive sanctions from the FA that may include an immediate suspension from all football, in addition to a potential criminal charge.
"..we take all reports of violent, aggressive and/or threatening behaviour very seriously."
The referee abandoned the game at Sawbridgeworth's ground in the 95th minute when the player allegedly went and found a knife and threatened the Clapton supporter, with claims the knife-wielder had been spat on.
A Clapton fan tweeted: "It appears a Clapton fan spat at an opposing player today. This is not what Clapton Ultras are about and we do not condone it."