Everton and West Ham are both appealing for witnesses after opposition players were hit by coins in their matches at the weekend.
Fulham midfielder Claus Jensen was struck during the game against the Toffees at Craven Cottage while Arsenal striker Robin van Persie was hit in his side's match away to West Ham.
The Football Association are to examine the referees' reports from both matches and are consulting with the clubs involved, and both Everton and West Ham have urged any fans with information to come forward.
Everton's head of PR and external affairs Ian Ross said: 'As a club we condemn without hesitation the actions of the moronic individual who threw a coin at Claus Jensen.
'We would urge anyone who knows his or her identity to contact the police immediately. We will be studying video recordings of the incident to see if we can firstly isolate and then identify the so-called supporter involved.'
Hammers managing director Paul Aldridge was also quick to condemn the attack on Van Persie.
'It goes without saying that there is no place in football for the kind of incident that occurred yesterday, and I am sure that all genuine West Ham United supporters feel the same way.
'We would be appalled if one of our own players were to be the victim of such an incident during a match, and so we will be doing everything we can to trace the individual who carried out this assault. Once we find them, they will be dealt with in the most severe way possible.
'As a football club, we are committed to doing all we can to ensure that Upton Park is a safe and sporting environment for all players, supporters and officials, and we will not let the actions of one person spoil that.'
An FA spokesman said: 'We will be looking at the referees' reports and speaking to the relevant clubs to see what steps they are taking to identify who is responsible.
'The key thing is to identify those responsible and make sure they are dealt with appropriately.'