Fake tickets for Adele's upcoming concert in Belfast are being sold on the Gumtree website, the PSNI has warned.
Detectives are investigating a internet scam involving the sale of counterfeit tickets over the last few weeks for Adele's SSE Arena gigs on February 29 and March 1, and Justin Bieber's in Dublin in 2016.
Police in Strabane have arrested a man and interviewed him about the scam.
He has been released on bail pending further enquiries.
Detective inspector Lindsey Kitson said police wanted anyone who had bought tickets for the concerts from a man after seeing an offer on website Gumtree to contact them on 101.
"As part of this ongoing investigation we want to ensure that we identify as many people as possible who may have been victims of this fraud," he said.
"We believe tickets for the Justin Bieber and Adele concerts were offered in a group of four from the Gumtree website and a subsequent transaction took place involving the exchange of money for fake tickets."