Northland police are urging concert-goers to get their tickets from a valid source as they believe up to four Whangārei people are selling dodgy tickets on Facebook.

Detective Sergeant Josh Lautogo said the Whangarei Tactical Crime Unit was investigating a number of complaints of online fraud from victims around New Zealand.

"Numerous complaints have been received from victims who have bought tickets to events and concerts via Facebook.

"Once they have paid for these tickets the seller has cut all contact and the tickets have never been received. This has left these victims out of pocket for large sums of