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 prime 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 organizing 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 has 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,” Hunt said. “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.”

Olympics sponsors Coca—Cola and Visa said they gave away most of their seating quotas to the public in promotional offers.

Coca—Cola said its competitions allowed prize winners “to choose the event they really wanted to attend.”

“We have also invited some long—standing partners, employees, and customers to attend the Games. We believe that usage levels of our tickets have been extremely high so far,” Coca—Cola said in a statement.

Visa said the “great majority” of its seats “are being used by ordinary cardholders who have won them through competitions or promotions.”

“We make great efforts to ensure that our ticket allocations are fully used,” the company said in a statement.

David Sparkes, chief executive of British Swimming, said the Olympic Acquatics 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 organizing 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.”

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

Separately, British police detained 18 people over suspected ticket fraud ahead of Friday’s opening ceremony and on Saturday, including a German man and a Slovakian woman charged over alleged attempts to illegally resell tickets to the opening ceremony.

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