The Football Association has launched an investigation after an assistant referee was hit by a firework during Tottenham's Barclays Premier League game at Aston Villa.
Two men were also arrested, police confirmed, after official David Bryan was struck by a flare or smoke bomb thrown from the visiting supporters' section at Villa Park on Sunday.
The incident occurred amid the celebrations after Andros Townsend had put Spurs on course for their 2-0 win with the opening goal after 31 minutes.
The restart was delayed as the smoking missile was removed but Bryan was unharmed and able to continue.
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.
"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 Andre Villas-Boas condemned the people responsible.
He said: "Obviously it is not great to see. It should be avoided completely. I think it touched the linesman.
"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."