Celtic have appealed to supporters to help identify the fan who threw a bottle onto the pitch during Sunday's Old Firm defeat at Ibrox.
The missile landed just yards from linesman David Doig during the second half and referee Kenny Clark is expected to mention the incident in his report.
Operations director George Douglas told the Celtic View: "A bottle was thrown onto the field of play in front of the Broomloan Stand and it is vital the culprit is found.
"Such behaviour is totally unacceptable to Celtic Football Club and demonstrates a complete lack of awareness of the serious trouble which the club could find itself in with the SFA as a consequence of the action.
"A full inquiry is being undertaken by the club and this 'fan' must be identified."
Named and shamed
The fan, if named and shamed, could face a ban from the club as Celtic look set to come down hard with the Scottish Football Association breathing down their neck.
Strathclyde Police will be assisting in the inquiry, by examining CCTV footage of the incident.
Park Gardens chiefs have admitted they were unlikely to take any further action Celtic or Rangers and that they were satisfied that the clubs would take appropriate action.
"I think any action being taken against both clubs is unlikely," said an SFA spokesman.
"The disciplinary committee is convinced that efforts have been and will be taken by the clubs to combat incidents like this that might occur in a game such as a Rangers-Celtic match.
"I am sure that stewarding and policing was to an extremely high level and the disciplinary committee are conscious of the steps being taken by the clubs."
http://news.bbc.co.uk/sport1/hi/scotland/1045713.stm