Tottenham are expected to receive a hefty fine after a linesman was hit by a flare during their 2-0 Barclays Premier League win at Aston Villa.
The Football Association has launched an investigation and two men were also arrested, police confirmed, after official David Bryan was struck by a flare thrown from the visiting supporters' section at Villa Park on Sunday.
The incident occurred amid the celebrations after Andros Townsend had opened the scoring on 31 minutes.
Bryan moments after he was hit by the smoke bomb
Bryan was unharmed and able to continue but the FA will now wait for referee Phil Dowd's report before deciding upon its next course of action.
A spokesman said: "The FA will investigate this matter, which is unacceptable.
"We will await the match officials' report and will be speaking to the clubs.
Linesman hit by flare
"Such incidents highlight the dangers of pyrotechnics being used in a football stadium."
Police officers and stewards moved in to remove supporters from the away fans section, which is housed in the Doug Ellis Stand.
Spurs boss André Villas-Boas condemned the people responsible.
He said: "I think situations like this do not have a place in football. I sincerely hope it does not happen again."
West Midlands Police later confirmed two men had been arrested in relation to the incident, which was also captured by a television camera.
"Police have arrested 2 men after a lit flare was thrown on the pitch during the Villa v Spurs game - the flare hit a linesman," a statement, released via Twitter, read.
"The two men aged 25 and 47 were arrested following the incident at Villa Park, fortunately the linesman wasn't injured."