The Football Association has launched a fresh investigation into coin-throwing after alleged incidents at both Stoke and QPR on Saturday.
An FA spokesman told Press Association Sport on Sunday that the governing body was "aware and investigating" after reports from the Britannia Stadium and Loftus Road.
An object was allegedly thrown at Stoke keeper Jack Butland during his side's 2-1 Premier League victory over Aston Villa, while QPR players celebrating Junior Hoilett's penalty during their 2-0 championship win over Birmingham were apparently targetted from the stand housing visiting supporters.
Rangers launched their own investigation immediately after the game, and the visitors promised stern action against anyone found responsible.
A QPR statement said: "Queens Park Rangers Football Club is aware of a coin throwing incident that took place during the first half of today's fixture against Birmingham City.
"A coin from the School End stand, in which the visiting supporters were situated, was thrown towards the Rangers players as the Rs celebrated their second goal in our Sky Bet Championship fixture at Loftus Road.
"The club will continue to review video footage and liaise with the Metropolitan and West Midlands police. The club will be making no further comment at this time."
A Birmingham spokesman said: "If anybody is found to have thrown a coin, we will take the strongest possible action. As a club, we utterly condemn that sort of behaviour.
"We will be liaising with the relevant bodies, including West Midlands Police, to investigate such allegations."
The FA was already looking into an incident in which West Brom's Chris Brunt was hit by a coin allegedly thrown by one of his club's own fans during last weekend's 3-1 FA Cup fifth-round defeat at Reading.
Police have made an arrest in connection with that matter.