Touts attempting to profit from Ariana Grande's benefit concert in Manchester on Sunday will have their tickets cancelled, the event's official ticketing company said.
Ticketmaster are performing regular checks across social media and said they were taking a "zero-tolerance" approach to online touting of the event, which is raising funds for victims of the Manchester Arena attack.
Stars including Justin Bieber, Katy Perry, Coldplay, Take That and Miley Cyrus will join Grande at the One Love Manchester concert with the £40 tickets snapped up in less than 20 minutes on Thursday.
Following the general sale, dozens of people were seen on social media and eBay offering to sell their tickets at an increased price after major secondary ticketing sites Seatwave, Get Me In, Viagogo and Stubhub all pledged to not allow the reselling of tickets on their websites.
eBay said they were immediately remove any listings attempting to profit unfairly from the terror attack which killed 22 people and left dozens more injured.
Ticketmaster said in a statement on their Twitter account: "We're working hard to get tickets direct to fans. We are cancelling tickets of those who are reselling wherever possible."
Earlier, they revealed all fans who attended Grande's targeted gig at the Manchester Arena will be given free passes to the benefit concert, regardless of where they purchased their tickets.
All net ticket proceeds of the show will go directly to the We Love Manchester Emergency Fund, set up by Manchester City Council in partnership with the British Red Cross to support grieving families and victims of the attack.
Michael Dugher, chief executive of industry body UK Music, praised the efforts to clamp down on touting.
The former culture, media and sport shadow secretary said: "It would be disgraceful to fleece fans using an occasion like this, charging a mark-up which would go in the touts' pockets rather than helping people caught up in this tragic event.
"We welcome the efforts of site operators to clamp down on resales and we would urge people to think twice about buying any tickets through social media or from touts outside the event on the night."