Organisers have launched an investigation into empty seats on the first day of the Olympics.
Television coverage has shown scores of empty seats, especially at the aquatics centre, the basketball arena and at Wimbledon for the tennis. There was also plenty of space in the Olympic Park.
On a school holiday and after months of public complaints over the inability of thousands in Britain to buy tickets, Britain's Culture Secretary Jeremy Hunt says he is disappointed by the empty seats.
Mr Hunt, the minister responsible for the Games, says organisers think they are mainly due to accredited seats that belong to sponsors.
But he says if they are not going to turn up, those tickets should be made available to the public.
On Saturday some ticket box offices at venues in the park still had queues of people seeking to buy tickets for selected sports.
The organising committee has declined to provide a figure for the number of people in the park on Saturday or how many tickets had been sold but said that 11 million people would attend the Games.
It said that many venues were packed and where there were empty seats, it would look at who should have been sitting in those seats and why they did not attend.
Early indications were that the empty places were in accredited seating areas, but a review would provide a fuller picture, the committee said.
Tickets were made available to the public in tranches before the Games and were regularly sold out.
A Reuters correspondent reports that, across the park, almost every visitor asked praised the ease of getting around, the lack of queues and the spacious feel of the park, the swift access to facilities, drinking water, open spaces and the friendliness of the staff.