The Football Association is to investigate after Manchester United keeper Roy Carroll was hit by a coin during the FA Cup win at Everton.
Carroll was felled after being hit in the 70th minute of Saturday's match, although he was able to continue.
Spokesman Adrian Bevington confirmed that the FA was speaking to Everton and to Merseyside Police.
"Individuals who throw missiles must face action from the police and through the courts and receive bans," he added.
Everton spokesman Ian Ross said the club was making CCTV and TV footage of the incident available to Merseyside Police.
"It would appear that the video recordings and footage we got prove quite conclusive," he said.
"The gentleman left the ground before the police could get him but we think with the video evidence we got we may be able to identify him.
"We are determined to find the individual in question and he will be banned for life if found guilty by the courts."
Wayne Rooney's return to his boyhood club for the first time since his £30m transfer to United had raised fears over crowd security.
And more than 30 football fans were arrested and five police officers injured as trouble flared in Liverpool on Saturday night.
Meanwhile, Everton will launch an investigation after Rooney was involved in a row with sponsors prior to the match.
The incident occurred as United striker Rooney left the field after his pre-match warm-up, when he was seen exchanging angry words with two members of the group of match-ball sponsors.
Everton's head of communications Ross said: "We view the situation very seriously and it will be investigated. We will want to hear the sponsors' side before taking any action."