West Ham and West Bromwich Albion are investigating a clash between Jake Livermore and home fans behind the visitors' bench at the London Stadium.
Livermore became embroiled in an angry exchange after being substituted in the second half and stepped into the stands in confrontation before he was led away to the dressing room by a member of the West Brom staff.
Albion manager Alan Pardew claimed the England midfielder had been provoked and coach John Carver remonstrated with the stewards charged with protecting the players on the bench before order was restored.