FIFA insist transport issues are responsible for the empty seats seen in differing quantities at the 2010 World Cup so far.
Rows of available space were visible in South Korea's match against Greece in Port Elizabeth on Saturday, and FIFA's head of media Nicolas Maingot attributed the problem to the failure of transport plans designed to get spectators with group bookings to the stadium.
He said: "Concerning Port Elizabeth there had been some tickets available in some numbers and we decided to make some group sales to large organisations, and we knew that when you do that you might face some no-show issues.
"We had been proactive (to prevent) that, organising specific transportation but it looks like this transportation has not worked 100 per cent or not worked properly, and we are working to make sure this is not the case for a few other of those games."
Maingot said the group sales were to South African businesses and that some had also been sold to the South African Football Association.
It was also confirmed that 700 tickets remained unsold for Sunday Algeria v Slovenia match in Polokwane - but the other games on Sunday, Serbia v Ghana in Pretoria and Germany v Australia in Durban, were reported as sell-outs.
FIFA ruled out the distribution of any unsold seats to local people and schoolchildren at late notice on security grounds.
Maingot and local organising committee spokesman Rich Mkhondo were happy with attendances overall and pointed out that the tournament average from the five games so far of 54,887 makes the tournament the second-best attended since 1982 - behind only USA 94 - although the averages for the other tournaments take in all the matches played rather than just the first five.
Problems with empty seats for the opening ceremony at Soccer City were attributed by Mkhondo to supporters' reluctance to put their faith in public transport, causing gridlock on approach roads as too many fans tried to get to the stadium by car.
He said: "Issues are being addressed but the onus is on supporters to arrive early and to use transport provided by the city.
"Event organisers will make sure we will try to resolve issues, we would like to appeal to supporters to use the transportation provided. Park your car, get into a bus and it will take 15 minutes to get into the stadium."
