Police arrested a teenage boy near Stamford Bridge after Chelsea's derby victory over Fulham on Saturday.
Officers were alerted to an individual displaying a weapon in the Fulham Broadway area.
A 16-year-old male was then detained on suspicion of carrying an imitation firearm.
talkSPORT has been told social media speculation of a mass shooting attempt is not true.
A Metropolitan Police spokesperson said: "A 16-year-old boy remains in police custody after he was arrested on suspicion of possession of an imitation firearm.
“The arrest occurred in Fulham Broadway at 14:41hrs on Saturday, 30 August after officers received information about a boy displaying a weapon and walking towards a crowded area.
“No one was injured in the incident.”
The Met Police are continuing their investigatio