Organizers of the London Olympics are investigating why there have been so many empty seats in the stands at multiple sporting events in the first days of competition.

Television images showed empty rows of seats at Wimbledon, the Aquatics Centre, soccer stadiums and other venues, prompting angry complaints from fans who were unable to purchase tickets.

British Culture Secretary Jeremy Hunt said blocks of the empty seats had been accredited to sponsors and that if they were not going to show up, then those tickets should be made available for the public.

In Sunday's events, National Basketball Association players Kobe Bryant of the Los Angeles Lakers and LeBron James of the Miami Heat face off against their French counterparts – some of whom are also NBA players. The French basketball roster includes the San Antonio Spurs' Tony Parker and Boris Diaw, and Portland Trail Blazer Nicolas Batum.

The women's gymnastic competitions also begins.

Saturday, U.S. swimmer Ryan Lochte won the 400-meter individual medley, defeating celebrated American swimmer Michael Phelps who came in fourth. It was the first time Phelps failed to win at least a bronze medal in an Olympic race.

In women's swimming, U.S. high school student Lia Neal used her school vacation to win a bronze medal, along with her teammates, in the 4-by-100-meter freestyle relay. Australia took home the gold, while the Netherlands clinched the silver.

The Olympic Games run through August 12.