Leaders of the London Olympics have vowed to find out why blocks of seats at highly sought events are lying empty and said they might set up new systems to ensure that those seats are filled, even if they have to be given away.

They were responding to widespread criticism from Saturday's opening day of competition, when whole sections of lower-tier seats were largely empty at events, including tennis, gymnastics and swimming. By contrast, an estimated 1 million people lined the route of Saturday's outdoor cycling, an unticketed and free event.

Sebastian Coe, chairman of the London Organising Committee, and British Culture Secretary Jeremy Hunt said they suspected that most of the no-shows were the guests of the games' corporate sponsors. Coe said the committee might name and shame those responsible if they don't take steps to get real fans in the seats.

"We think it was accredited seats that belonged to sponsors. But if they're 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're looking at this very urgently,'' Hunt said.

Resale option

David Sparkes, chief executive of British Swimming, said the Olympic Aquatics Centre was much fuller in the evening than the morning heats. But he suggested that the Olympics should create a facility whereby holders of tickets who won't use them can donate them immediately to a charity for resale.

"We all like to see a full house. The pool is one of the most sought-after venues and tickets are hard to come by,'' Sparkes said.

The London Games Organising Committee said in a statement emailed to The Associated Press it is looking into "who should have been sitting in the seats, and why they did not attend''.

Hunt said London organisers had learned from Beijing in 2008, which had problems filling some venues because of the high cost of tickets.

"One of the lessons that we took away... is that full stadia create the best atmosphere, it's best for the athletes, it's more fun for spectators, and it's been an absolute priority.''

He noted that the London Games does feature a facility whereby fans leaving a stadium can turn in their tickets to be used by other fans on standby, but he said other systems to redistribute tickets would be considered.

"We want this to be the Olympics that people remember for the best atmosphere,'' he said.