Fans who purchased tickets for synchronised swimming at London 2012 could instead be handed seats at some of the Games’ blue-chip events due to an administrative error.

London 2012’s Organising Committee was on Wednesday forced to concede that about 10,000 extra tickets had been sold in the second online offering last year, affecting thousands of consumers who had been asked to swap events. While fans may now end up with tickets for high-profile events such as the 100 metres final or swimming medal heats, the news comes as an embarrassing blow to organisers, with ticketing proving to be one of London 2012’s main challenges.

“As a result of finalising the seating configurations in our venues and reconciling the millions of Olympic and Paralympic ticket orders against the seating plans for around 1,000 sporting sessions, we have discovered an error in seats available in four synchronised swimming sessions,” said a spokesperson for the Organising Committee, according to Reuters. “In December we contacted around 3,000 customers who had applied for tickets in the four sessions during the second round sales process. We are exchanging their synchronised swimming tickets for tickets in other sports that they originally applied for.”

Although the Olympics’ blue-chip events sold out immediately in the first round of ticket sales, a batch of attractive seats have been retained for sale in May once venues have completed their final tests. London 2012 has stated that the seats being swapped for the synchronised swimming will come from this final batch of around a million tickets.