Scotland striker Billy Dodds was almost hit by the missile when it was thrown from the visitors' end as the player celebrated his goal in the home side's surprise 2-1 victory.
It was one of a number of bad-tempered incidents during the encounter, with two coaches carrying Dundee United supporters coming under attack as they tried to leave the ground after the match.
Celtic have called on supporters to name the fans involved and promised that the offenders will be banned from Parkhead for life once they are caught.
The SFA yesterday received the report of the game's referee, Jim Clark, in which he made reference to the incident.
"It mentions a missile-throwing incident so we will be writing to both clubs for their comments," said Andy Mitchell, the SFA spokesman.
"We would urge supporters with any information on the incident to come forward," said the Celtic public relations chief, Peter McLean. "It was an act of sheer stupidity and we will be carrying out our own investigation into the incident. These acts will simply not be tolerated."
With a pounds 45,000 fine having been imposed on them following the disturbances at the controversial Old Firm game in May, when the referee Hugh Dallas was struck on the head by a coin thrown by a Celtic supporter, the latest setback is one the Parkhead club could well do without.
Aberdeen are giving a trial to Bruges defender Pascal Renier. The 28- year-old, six-foot centre-half will link up with the Dons squad this week as their manager, Ebbe Skovdahl, seeks to end his woeful start to the season.
Steve Bruce yesterday made veteran defender Ken Monkou his eighth signing since taking over the reins at Huddersfield during the close season.
Monkou, 34, has agreed a three-month contract after leaving Southampton and that deal is expected to be extended in due course.
The Derby County manager, Jim Smith, will sign Lee Morris from Sheffield United in a pounds 3m deal today - despite the fact he has a broken foot.
Smith made his bid yesterday and wants speedy England Under-21 forward Morris tied up quickly although he will not be fit to play for a couple of weeks.
The Derby boss has agreed the price with the Blades and Morris will sign a contract subject to passing a medical when he is fully fit.
Morris has only played a handful of games for United, but is rated one of the brightest prospects around. Smith wants to bring in new faces after a poor start to the season when his lack of attacking options has reduced Derby's threat.
Leeds have still not received the pounds 6m first instalment from Atletico Madrid for striker Jimmy Floyd Hasselbaink. But the Elland Road chairman, Peter Ridsdale, is confident that the transfer saga of the Dutchman is finally over.
Hasselbaink quit Leeds in a pounds 12m deal days before the start of the season, but a Spanish Bank Holiday apparently prevented the money arriving on Monday. "I am told it is on its way but it hasn't cleared with the bank yet. However, I think everything is resolved," Ridsdale said.Reuse content