Motherwell are “very disappointed” after a plastic bottle was thrown towards an assistant referee in Thursday’s 1-0 Europa Conference League qualifying defeat by Sligo Rovers.
The incident took place near the end of Well’s 1-0 first-leg loss.
The Fir Park club praised fans who “turned out in great numbers” and acknowledged “several issues relating to ticketing/seating”.
More than 7,000 supporters attended, with the return in Sligo next Thursday.
“Over the last few seasons there have been a couple of occasions where objects have been thrown onto the field of play at Fir Park,” the club said on their website.
“Our policy has always been to deal with individuals quietly and efficiently, and we have handed out indefinite bans to those who we have been able to identify.
“To put it into some context, we are talking about a very small number of flash points over a few seasons, and the overwhelming majority of ‘Well fans who follow the team are passionate, noisy and colourful, but do not overstep the mark by endangering players, officials or staff.
“The incident last night is now being investigated by Uefa and the likelihood is the club will be punished.
“We ourselves will work hard to identify the person responsible and will take firm action. It goes without saying, but throwing any objects onto the pitch is unacceptable at Fir Park or any other football stadium.”