Olympic organiser Locog has launched an urgent investigation into the large number of vacant seats at some Olympic venues on the first day of the 2012 London Olympics.
Rows of vacant seats were visible at a number of venues including the Aquatics Centre, basketball arena and at Wimbledon for tennis. Seats were also unoccupied at gymnastics, handball, volleyball and badminton venues.
Culture Secretary Jeremy Hunt said he was disappointed at the number of empty seats.
"Locog are doing a full investigation into what happened," Hunt told BBC television.
"It's a shame this happened, but we are going to do everything we can to make sure we fill up these stadia."
Seats remain vacant at a time when members of the public are desperate to get tickets. Some people paid £2,012 for top-price tickets to the opening ceremony on 27 July.
In contrast, huge crowds gathered in the streets to cheer on cyclists, and in public parks to watch events unfold on specially erected giant screens.
"I thought the least I could do was go and see them [the gymnasts], and I'm watching them on television and the place is half empty and that's a shame. I would have paid whatever it takes to see them," one gymnastics enthusiast told Reuters.
The vacant seats are believed to have been allocated to official bodies, sponsors and the media.
"We think it was accredited seats that belong to sponsors, but if they are not going to turn up, we want those tickets to be available for members of the public, because that creates the best atmosphere. So we are looking at this very urgently," Hunt said.
Organisers sold a total of seven million Olympic tickets, out of a total 8.8 million tickets by early June. Locog is believed to have held back nearly 550,000 tickets for last-minute sale or allocation.
"Where there are empty seats, we will look at who should have been sitting in the seats, and why they did not attend. Early indications are that the empty seats are in accredited seating areas, but this is day one, and our end of day review will provide a fuller picture," Locog said in a statement.