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. Al Jazeera's Jonah Hull reports from London.