Companies that sell tickets for concerts and other live events are facing a probe from the State's competition watchdog.
It is understood that the investigation involves the main providers of tickets for live events, venues and concert promoters.
The Competition and Consumer Protection Commission said it had launched an investigation into suspected breaches of competition law in relation to the provision of tickets and the operation of ticketing services for live events.
The move comes after Ticketmaster was heavily criticised earlier this month when ticket sales it was handling for an upcoming U2 concert in Croke Park sold out in minutes.
Concert goers were annoyed when the tickets soon appeared on its sister site Seatwave for multiples of the original price.
In some cases, sellers have asked for up to €1,000 for a ticket.
The commission on the re-sale of tickets on some sites can be up 20pc, the Dáil was told recently.
The competition probe will "focus primarily on potentially anti-competitive conduct by operators, including those involved in providing tickets and ticketing services, promoters and venues," the Competition and Consumer Protection Commission said in a statement.
It wants to hear from anyone in the sector with information they feel is relevant.
Ticketmaster said it has no comment to make on the Commission's announcement.
Live Nation, the entertainment conglomerate which controls Ticketmaster and Seatwave, did not comment. Live Nation UK and Ireland is headed by promoter Denis Desmond, of MCD Promotions.
Aiken Promotions did not respond when asked to comment.
Last week, Fine Gael backbencher Noel Rock said he was preparing a bill to clamp down on mass ticket re-selling.
He wants to change the rules on ticket sales, saying there was technology to prevent such large-scale re-selling.