Olympic organizers are investigating why rows of seats at some venues were empty on the first full day of competition at the London Games.

Cameras captured rows of vacant spots for swimming heats, volleyball, gymnastics and equestrian events on the opening day of the Games on Saturday, even though the events were supposedly sold-out.

Britain's Culture Secretary Jeremy Hunt called the development "very disappointing" and said he believes the empty seats were set aside for so-called Olympic family members, which includes corporate sponsors, IOC members and their famlies, athletes and other accredited officials.

Hunt suggested the empty seats could be offered to members of the public.

More prime seats were left empty Sunday at events that included beach volleyball and women's gymnastics.

BBC Olympics correspondent James Pearce retweeted a comment from someone who posted a photo of empty seats at the North Greenwich Arena and who described the scene as "disgraceful."

It appears the empty seats were largely in lower-tier VIP seating areas. The top tiers were "packed to the rafters" with "real fans" who should be allowed to move down after 10 minutes, the Twitter posting said.

"This is exactly what London organizers were trying to avoid because it's an ongoing problem," CBC's Heather Hiscox reported from London. "It was in Athens. It was particular bad in Beijing, and here in London, they said it would not be the situation, they would not allow it."

Sebastian Coe, head of the London Organizing Committee of the Olympic Games, is not naming or shaming the people who were not in the seats, but he did express his concerns at a news conference Sunday.

"We take it seriously," Coe told reporters. "That's why we will make sure where we possibly can that we get people into those seats when they're not being used."

Organizers say they plan to call in soldiers, teachers and school children to fill some of the prime, empty seats.