Everton forward Richarlison gave Everton a massive relegation lifeline with the vital winner against Chelsea.
But the Brazilian ace faces a potential three-match ban for his celebration.
The South American capitalised on Cesar Azpilicueta’s blunder to claim all three points for Frank Lampard’s men.
It means the Toffees are just two points adrift of safety with a game in hand over both Leeds and Burnley.
But the striker is in hot water with the FA after picking up a lit blue flare and throwing it back into the crowd.
FA chiefs confirmed a probe was likely to be launched when they receive the reports from referee Kevin Friend and Prem match day delegates.
Wembley officials were alerted to the video evidence and a charge appears almost certain.
That could bring a three-match ban, dealing a huge blow to Everton’s survival hopes.
But FA regulations over a “non-standard” incident mean punishment is unlikely to come into effect for at least a fortnight.
And while the maximum penalty would be a three-match suspension, Richarlison might escape with a fine and severe warning.
The FA’s next step is unlikely to happen before Tuesday because of the Bank Holiday tomorrow.
An Everton club spokesperson said: “We will look into the matter but, as far we we are concerned, Richarlison was attempting to throw it out of the ground.”
In 2002, Liverpool defender Jamie Carragher was issued with a formal police warning after hurling a coin back into the crowd against Arsenal.
Liverpool also fined him £40,000 after the incident at Highbury.
Earlier this year, the FA wrote to Liverpool’s Harvey Elliot after he was seen handling a flare following the Carabao Cup Final, which the Reds won on penalties