West Ham are investigating claims striker Andy Carroll and goalkeeper Darren Randolph were drunk on Tuesday afternoon.
Pictures of the pair circulated on social media, following a club sanctioned night out on Monday.
The Hammers have lost five of their six Premier League games this season, including four in a row, and play Middlesbrough on Saturday at the London Stadium.
A West Ham United spokesman said: "The club will be looking into these allegations and will deal with the players as we see fit."
Carroll, who is sidelined with a knee injury, posted a series of statements on Twitter, with fans replying asking if he was drunk.
When it was suggested he was, in fact, in a coffee shop, Carroll replied: "I seriously need to sort my parties out!! Sorry lads."
He added: "Back in the day my parties had the wish I was there effect!"
One Twitter user and West Ham fan posted a photo of Carroll and Randolph and said the pair "appear to be enjoying themselves".
But in subsequent replies to other fans, the Twitter user admitted he had not taken the photo.