Rangers have condemned “in the strongest possible terms” the incident in which Celtic's Arne Engels was struck by a coin during the Old Firm match on Thursday.
The substitute fell to the ground and needed treatment after suffering a knock when taking a corner kick towards the end of Rangers' 3-0 win.
There were no Celtic fans inside Ibrox Stadium due to an ongoing row over the distribution of tickets outside the stadium, and Rangers said they would assist police with their investigation.
Celtic boss Brendan Rodgers confirmed that Ingles was “fine” but added that “with an inch less, he would have been hit straight in the eye”.
This incident came near the end of the derby match, which reduced the gap with Celtic at the top of the Scottish Premiership to 11 points, and could leave Rangers facing a penalty.
Celtic defender Alistair Johnstone saw Ingles being beaten and warned “everyone to be smart” during matches.
The defender added: “They are human beings, someone's son, so let's refrain from throwing things at men's heads.”