West Brom midfielder Jake Livermore was escorted down the tunnel at West Ham's London Stadium on Tuesday night after a clash with a fan, the Mirror have reported.
The England international was withdrawn in the second-half of his side's 2-1 defeat, replaced by Hal Robson-Kanu.
Witnesses reportedly saw Livermore involved in a heated confrontation with a home supporter, before he was ushered away.
Stewards surrounded the tunnel after the incident, while West Brom coach John Carver remonstrated with officials.
“The only thing I know is that I saw Jake in the crowd which disturbed me a bit," said Baggies boss Alan Pardew after the game - quoted by the Birmingham Mail. "He wouldn’t have done that unless he was provoked severely. I’ll talk to him and we’ll go from there.
“Of course [we’ll investigate it]. I haven’t had a chance to speak to Jake, I’ll speak to Jake and we’ll go from there.”
Livermore, who joined West Brom last summer, tested positive for cocaine in April 2015, although it was later revealed that he had taken the substance to help with the grief of the death of his newborn child.
The 28-year-old made his 22nd appearance of the season against West Ham, but was unable to inspire his side to victory while on the pitch.
(You may also be interested in West Brom Boss Pardew Blames Cramped Fixture List After Narrow West Ham Defeat)
The visitors led through James McClean but a brace from Andy Carroll, including a 94th minute winner, left them without a point.
Pardew's side now sit in 19th place, only above Swansea on goal difference, and four points from safety.