Folk rockers Mumford & Sons reached out to fans on Thursday (22Nov12) after learning a number of fake tickets were circulated for their show in Portsmouth, England.
The band played at the city's Guildhall on Thursday night, but 100 gig-goers were turned away because they did not have valid stubs for the concert.
Bosses at the venue revealed they are now working with police to investigate the issue, and the musicians took to their website to address the mix-up.
A post on the site reads, "We sincerely hope that not too many of you good honest Mumford & Sons fans have been affected.
"If you have purchased tickets from any secondary vendors then we would urge you to seek your money back immediately. Remember to always purchase tickets from official vendors only."