Rangers have condemned the "moronic behaviour" of supporters alleged to have racially abused Maurice Edu after last night's Champions League thrashing by Unirea Urziceni.
United States midfielder Edu, 23, played no part in the 4-1 Group G defeat but watched the match at Ibrox and says he was targeted by his own club's supporters as he left the stadium.
A statement released by the Ibrox club read: "Rangers Football Club condemns out of hand this moronic behaviour.
"The action of this individual is disgusting and completely unacceptable.
"It is extremely disappointing that people such as this attach themselves to the wider Rangers support and tarnish the image of the club and its fans.
"The club will now undertake a full investigation to identify the individual in question and take appropriate action.
"We would urge anyone who has information on the identity of the individual responsible to contact the club immediately.
"Everyone associated with Rangers will once again demonstrate their on-going commitment to Show Racism the Red Card as we support the Weekend of Action at the Hibernian game at Ibrox Stadium on Saturday."
Edu wrote a message on his Twitter feed which read: "Not sure what hurt more: result last nite or being racially abused by couple of r own fans as I'm getting in my car."
The Rangers Supporters Trust condemned anyone who might have abused Edu, who has been out all season with a knee injury.
RST spokesman David Edgar told Press Association Sport: "We would absolutely condemn that if that's the case.
"These are not Rangers fans and they should be caught and prosecuted to the full extent of the law."
Billy Singh, Campaign Manager for Show Racism the Red Card, said: "The racial abuse suffered by Maurice Edu last night was totally unacceptable.
"Would the same fans have reacted in the same way if he had scored the winning goal last night?
"It proves that as a society we have a long way to go to eradicate this type of behaviour.
"Official statistics show that on average there are 14 reported incidents a day.
"Anecdotal evidence suggests that 80% goes unreported.
"Football is leading the way in trying to change peoples attitudes and behaviour within football grounds.
"I call upon fans of all Scottish clubs to challenge this type of behaviour not only within football but in society in general. Show Racism the Red Card will continue to spread the anti-racist message in football but also in communities throughout Scotland."